diff --git a/btrbk b/btrbk
index b46eb6b..9f9798d 100755
--- a/btrbk
+++ b/btrbk
@@ -285,7 +285,6 @@ my $quiet;
 my @exclude_vf;
 my $do_dumper;
 my $show_progress = 0;
-my $err = "";
 my $output_format;
 my $lockfile;
 my $tlog_fh;
@@ -294,6 +293,7 @@ my $current_transaction;
 my @transaction_log;
 my %config_override;
 my @tm_now;  # current localtime ( sec, min, hour, mday, mon, year, wday, yday, isdst )
+my @stderr;  # stderr of last run_cmd
 my %warn_once;
 my %kdf_vars;
 my $kdf_session_key;
@@ -687,16 +687,15 @@ sub run_cmd(@)
 
   my @cmd_pipe_in = (ref($_[0]) eq "HASH") ? @_ : { @_ };
   die unless(scalar(@cmd_pipe_in));
-  $err = "";
+  @stderr = ();
 
   my $destructive = 0;
-  my $catch_stderr = 0;
-  my $exitcode_loglevel = "debug";
-  my $filter_stderr = undef;
   my @cmd_pipe;
   my @unsafe_cmd;
   my $compressed = undef;
   my $stream_options = $cmd_pipe_in[0]->{stream_options} // {};
+  my @filter_stderr;
+  my $fatal_stderr;
   my $has_rsh;
 
   $cmd_pipe_in[0]->{stream_source} = 1;
@@ -706,10 +705,9 @@ sub run_cmd(@)
   {
     die if(defined($href->{cmd_text}));
 
-    $catch_stderr = 1 if($href->{catch_stderr});
-    $filter_stderr = $href->{filter_stderr} if($href->{filter_stderr});  # NOTE: last filter wins!
+    push @filter_stderr, ((ref($href->{filter_stderr}) eq "ARRAY") ? @{$href->{filter_stderr}} : $href->{filter_stderr}) if($href->{filter_stderr});
+    $fatal_stderr = $href->{fatal_stderr} if($href->{fatal_stderr});
     $destructive = 1 unless($href->{non_destructive});
-    $exitcode_loglevel = $href->{exitcode_loglevel} if($href->{exitcode_loglevel});
     $has_rsh = 1 if($href->{rsh});
 
     if($href->{check_unsafe}) {
@@ -819,15 +817,15 @@ sub run_cmd(@)
 
 
   # execute command
-  my ($pid, $out_fh, $err_fh, @stdout, @stderr);
+  my ($pid, $out_fh, $err_fh, @stdout);
   $err_fh = gensym;
   if(eval_quiet { $pid = open3(undef, $out_fh, $err_fh, $cmd); }) {
     chomp(@stdout = readline($out_fh));
     chomp(@stderr = readline($err_fh));
     waitpid($pid, 0);
     if($loglevel >= 4) {
-      TRACE "[stdout] $_" foreach(@stdout);
-      TRACE "[stderr] $_" foreach(@stderr);
+      TRACE map("[stdout] $_", @stdout);
+      TRACE map("[stderr] $_", @stderr);
     }
   }
   else {
@@ -847,26 +845,22 @@ sub run_cmd(@)
   }
   my $exitcode = $? >> 8;
 
-  my @filtered_err;
-  if($filter_stderr) {
-    @filtered_err = map { &{$filter_stderr} ($exitcode) // () } @stderr;
+  # call hooks: fatal_stderr, filter_stderr
+  if(($exitcode == 0) && $fatal_stderr) {
+    $exitcode = -1 if(grep &{$fatal_stderr}(), @stderr);
   }
-  elsif($has_rsh && ($exitcode == 255)) {
-    # SSH returns exit status 255 if an error occurred.
-    @filtered_err = map { { error => $_ } } @stderr;
-    $exitcode_loglevel = "error";
+  foreach my $filter_fn (@filter_stderr) {
+    @stderr = map { &{$filter_fn} ($exitcode); $_ // () } @stderr;
   }
 
-  if($exitcode || (grep { $_->{fatal} } @filtered_err)) {
-    my $log_text = "Command execution failed (exitcode=$exitcode): `$cmd`";
-    $exitcode_loglevel = "error" if(scalar(@filtered_err));
-    if($exitcode_loglevel eq "error")   { ERROR $log_text; }
-    elsif($exitcode_loglevel eq "warn") { WARN  $log_text; }
-    else                                { DEBUG $log_text; }
-    foreach(@filtered_err) {
-      ERROR "... $_->{error}" if(defined($_->{error}));
-      WARN  "... $_->{warn}"  if(defined($_->{warn}));
-      DEBUG "... $_->{debug}" if(defined($_->{debug}));
+  unshift @stderr, "sh: $cmd";
+
+  if($exitcode) {
+    my @log_text = ("Command execution failed (exitcode=$exitcode): `$cmd`", map("... $_", @stderr));
+    if($has_rsh && ($exitcode == 255)) { # SSH returns exit status 255 if an error occurred.
+      ERROR @log_text;
+    } else {
+      DEBUG @log_text;
     }
     return undef;
   }
@@ -877,13 +871,25 @@ sub run_cmd(@)
 }
 
 
+sub _btrfs_filter_stderr
+{
+  if(/^usage: / || /(unrecognized|invalid) option/) {
+    WARN_ONCE "Using unsupported btrfs-progs < v$BTRFS_PROGS_MIN";
+  }
+  # strip error prefix (we print our own)
+  # note that this also affects ssh_filter_btrbk.sh error strings
+  s/^ERROR: //;
+}
+
+
 sub btrfs_filesystem_show($)
 {
   my $vol = shift || die;
   my $path = $vol->{PATH} // die;
   return run_cmd( cmd => vinfo_cmd($vol, "btrfs filesystem show", { unsafe => $path } ),
                   rsh => vinfo_rsh($vol),
-                  non_destructive => 1
+                  non_destructive => 1,
+                  filter_stderr => \&_btrfs_filter_stderr,
                  );
 }
 
@@ -894,7 +900,8 @@ sub btrfs_filesystem_df($)
   my $path = $vol->{PATH} // die;
   return run_cmd( cmd => vinfo_cmd($vol, "btrfs filesystem df", { unsafe => $path }),
                   rsh => vinfo_rsh($vol),
-                  non_destructive => 1
+                  non_destructive => 1,
+                  filter_stderr => \&_btrfs_filter_stderr,
                  );
 }
 
@@ -905,8 +912,14 @@ sub btrfs_filesystem_usage($)
   my $path = $vol->{PATH} // die;
   my $ret = run_cmd( cmd => vinfo_cmd($vol, "btrfs filesystem usage", { unsafe => $path } ),
                      rsh => vinfo_rsh($vol),
-                     non_destructive => 1
+                     non_destructive => 1,
+                     filter_stderr => \&_btrfs_filter_stderr,
                     );
+  unless(defined($ret)) {
+    ERROR "Failed to fetch btrfs filesystem usage for: $vol->{PRINT}", map("... $_", @stderr);
+    return undef;
+  }
+
   return undef unless(defined($ret));
 
   my %detail;
@@ -978,21 +991,7 @@ sub btrfs_subvolume_show($;@)
   my $ret = run_cmd(cmd => vinfo_cmd($vol, "btrfs subvolume show", @cmd_options, { unsafe => $path }),
                     rsh => vinfo_rsh($vol),
                     non_destructive => 1,
-                    catch_stderr => 1, # hack for shell-based run_cmd()
-                    filter_stderr => sub {
-                      return undef unless($_[0]); # do nothing if exitcode=0
-                      if(s/^ERROR: //) { # catch errors from btrfs-progs as well as ssh_filter_btrbk.sh
-                        $err = $_;
-                        return { error => $_, fatal => 1 } if(/^ssh_filter_btrbk.sh/); # "fatal" causes run_cmd to return undef
-                      } elsif(/(unrecognized|invalid) option/) {
-                        WARN_ONCE "$_ (maybe using unsupported btrfs-progs < v$BTRFS_PROGS_MIN " . ($vol->{HOST} ? "on host=$vol->{HOST} " : "") . "?)";
-                      } else {
-                        DEBUG "Unparsed error: $_";
-                        $err ||= $_;
-                      }
-                      # soft fail: $err can be displayed as a user-friendly WARNING
-                      return undef;
-                    },
+                    filter_stderr => \&_btrfs_filter_stderr,
                    );
 
   return undef unless(defined($ret));
@@ -1103,6 +1102,7 @@ sub btrfs_subvolume_list_readonly_flag($)
   my $ret = run_cmd(cmd => vinfo_cmd($vol, "btrfs subvolume list", '-a', '-r', { unsafe => $path } ),
                     rsh => vinfo_rsh($vol),
                     non_destructive => 1,
+                    filter_stderr => \&_btrfs_filter_stderr,
                    );
   return undef unless(defined($ret));
 
@@ -1135,6 +1135,7 @@ sub btrfs_subvolume_list($;@)
   my $ret = run_cmd(cmd => vinfo_cmd($vol, "btrfs subvolume list", @filter_options, @display_options, { unsafe => $path } ),
                     rsh => vinfo_rsh($vol),
                     non_destructive => 1,
+                    filter_stderr => \&_btrfs_filter_stderr,
                    );
   return undef unless(defined($ret));
 
@@ -1219,9 +1220,10 @@ sub btrfs_subvolume_find_new($$;$)
   my $ret = run_cmd(cmd => vinfo_cmd($vol, "btrfs subvolume find-new", { unsafe => $path }, $lastgen ),
                     rsh => vinfo_rsh($vol),
                     non_destructive => 1,
+                    filter_stderr => \&_btrfs_filter_stderr,
                    );
   unless(defined($ret)) {
-    ERROR "Failed to fetch modified files for: $vol->{PRINT}";
+    ERROR "Failed to fetch modified files for: $vol->{PRINT}", map("... $_", @stderr);
     return undef;
   }
 
@@ -1285,10 +1287,11 @@ sub btrfs_subvolume_snapshot($$)
                    );
   my $ret = run_cmd(cmd => vinfo_cmd($svol, "btrfs subvolume snapshot", '-r', { unsafe => $src_path }, { unsafe => $target_path } ),
                     rsh => vinfo_rsh($svol),
+                    filter_stderr => \&_btrfs_filter_stderr,
                    );
   end_transaction("snapshot", defined($ret));
   unless(defined($ret)) {
-    ERROR "Failed to create btrfs subvolume snapshot: $svol->{PRINT} -> $target_path";
+    ERROR "Failed to create snapshot: $svol->{PRINT} -> $target_path", map("... $_", @stderr);
     return undef;
   }
   return $target_vol;
@@ -1338,45 +1341,35 @@ sub btrfs_subvolume_delete($@)
     }
     $ret = run_cmd(cmd  => ['rm', '-f',  @cmd_target_paths ],
                    rsh  => vinfo_rsh($targets->[0]),
-                   catch_stderr => 1, # hack for shell-based run_cmd()
-                   filter_stderr => sub {
-                     # catch errors from "rm -f"
-                     if(/^rm: cannot remove '($file_match)':/) {
-                       my $catch = $1; # make sure $catch matches $vol->{PATH}
-                       $catch =~ s/\.info$//;
-                       $catch =~ s/\.split_[a-z][a-z]$//;
-                       $err_catch{$catch} //= [];
-                       push(@{$err_catch{$catch}}, $_);
-                       return undef; # no error messages in run_cmd
-                     }
-                     else {
-                       # show errors in run_cmd; force "Command execution failed" error message
-                       return { error => $_, fatal => 1 };
-                     }
-                   },
                   );
+    unless(defined($ret)) {
+      foreach(@stderr) {
+        next unless(/^rm: cannot remove '($file_match)':/);
+        my $catch = $1; # make sure $catch matches $vol->{PATH}
+        $catch =~ s/\.info$//;
+        $catch =~ s/\.split_[a-z][a-z]$//;
+        $err_catch{$catch} //= [];
+        push(@{$err_catch{$catch}}, $_);
+      }
+    }
   }
   else {
     my @cmd_target_paths = map { { unsafe => $_->{PATH} } } @$targets;
-    my $unparsed_errors;
     my @options;
     @options = ("--commit-$commit") if($commit);
     $ret = run_cmd(cmd => vinfo_cmd($targets->[0], "btrfs subvolume delete", @options, @cmd_target_paths ),
                    rsh => vinfo_rsh($targets->[0]),
-                   catch_stderr => 1, # hack for shell-based run_cmd()
-                   filter_stderr => sub {
-                     return undef unless(s/^ERROR: //); # strip ERROR prefix
-                     if(/'($file_match)'/ || /: ($file_match)$/ || /($file_match):/) {
-                       # NOTE: as of btrfs-progs-4.16, this does not catch anything
-                       $err_catch{$1} //= [];
-                       push(@{$err_catch{$1}}, $_);
-                     } else {
-                       $unparsed_errors = 1;
-                     }
-                     return undef; # no error messages in run_cmd
-                   },
+                   fatal_stderr  => sub { m/^ERROR: /; },  # probably not needed, "btrfs sub delete" returns correct exit status
+                   filter_stderr => \&_btrfs_filter_stderr,
                   );
-    $ret = undef if($unparsed_errors);
+    unless(defined($ret)) {
+      foreach(@stderr) {
+        next unless(/'($file_match)'/ || /: ($file_match)$/ || /($file_match):/);
+        # NOTE: as of btrfs-progs-4.16, this does not catch anything
+        $err_catch{$1} //= [];
+        push(@{$err_catch{$1}}, $_);
+      }
+    }
   }
 
   if(defined($ret)) {
@@ -1388,7 +1381,7 @@ sub btrfs_subvolume_delete($@)
       foreach my $check_target (@$targets) {
         my $err_ary = $err_catch{$check_target->{PATH}};
         if($err_ary) {
-          ERROR "Failed to delete subvolume \"$check_target->{PRINT}\": $_" foreach(@$err_ary);
+          ERROR map("Failed to delete subvolume \"$check_target->{PRINT}\": $_", @$err_ary);
           $catch_count++;
         }
         else {
@@ -1398,9 +1391,9 @@ sub btrfs_subvolume_delete($@)
       @deleted = () if($catch_count != (scalar keys %err_catch));
     }
     unless(scalar(@deleted)) {
-      ERROR "Failed to match error messages from delete command, assuming nothing deleted:";
-      ERROR "... possibly not deleted subvolume: $_" foreach(map( { $_->{PRINT} } @$targets));
-      ERROR "... consider running 'btrbk prune -n'";
+      ERROR "Failed to match error messages from delete command, assuming nothing deleted", map("... $_", @stderr);
+      ERROR map("Possibly not deleted subvolume: $_->{PRINT}", @$targets);
+      ERROR "Consider running 'btrbk prune -n'";
     }
   }
 
@@ -1426,10 +1419,11 @@ sub btrfs_qgroup_destroy($@)
                     vinfo_prefixed_keys("target", $vol));
   my $ret = run_cmd(cmd => vinfo_cmd($vol, "btrfs qgroup destroy", $qgroup_id, { unsafe => $path }),
                     rsh => vinfo_rsh($vol),
+                    filter_stderr => \&_btrfs_filter_stderr,
                    );
   end_transaction($opts{type} // "qgroup_destroy", defined($ret));
   unless(defined($ret)) {
-    ERROR "Failed to destroy qgroup \"$qgroup_id\" for subvolume: $vol->{PRINT}";
+    ERROR "Failed to destroy qgroup \"$qgroup_id\" for subvolume: $vol->{PRINT}", map("... $_", @stderr);
     return undef;
   }
   return $vol;
@@ -1472,21 +1466,14 @@ sub btrfs_send_receive($$;$$$)
     rsh => vinfo_rsh($snapshot, disable_compression => $stream_options->{stream_compress}),
     name => "btrfs send",
     stream_options => $stream_options,
-    exitcode_loglevel => "error", # print error message if exitcode != 0
-    catch_stderr => 1, # hack for shell-based run_cmd()
+    filter_stderr => [ \&_btrfs_filter_stderr, sub { $_ = undef if(/^At subvol/) } ],
   };
 
   push @cmd_pipe, {
     cmd => vinfo_cmd($target, "btrfs receive", @receive_options, { unsafe => $target_path . '/' } ),
     rsh => vinfo_rsh($target, disable_compression => $stream_options->{stream_compress}),
     name => "btrfs receive",
-    catch_stderr => 1, # hack for shell-based run_cmd()
-    filter_stderr => sub {
-      # NOTE: btrfs-progs < 4.11: if "btrfs send" fails, "btrfs receive" returns 0!
-      return { error => $_, fatal => 1 } if(s/^ERROR: //); # "fatal" causes run_cmd to return undef
-      return { warn  => $_ } if(s/^WARNING: //);
-      return undef;
-    },
+    fatal_stderr  => sub { m/^ERROR: /; }, # NOTE: btrfs-progs < 4.11: if "btrfs send" fails, "btrfs receive" returns 0!
   };
 
   my $send_receive_error = 0;
@@ -1496,7 +1483,9 @@ sub btrfs_send_receive($$;$$$)
                     vinfo_prefixed_keys("parent", $parent),
                    );
   my $ret = run_cmd(@cmd_pipe);
+  my @cmd_err;
   unless(defined($ret)) {
+    @cmd_err = @stderr; # save for later
     $send_receive_error = 1;
   }
 
@@ -1522,21 +1511,21 @@ sub btrfs_send_receive($$;$$$)
       unless($send_receive_error) {
         # plausibility checks on target detail
         unless($detail->{readonly}) {
-          ERROR "[send/receive] target is not readonly: $vol_received->{PRINT}";
+          push @cmd_err, "target is not readonly: $vol_received->{PRINT}";
           $send_receive_error = 1;
         }
         if($detail->{received_uuid} && ($detail->{received_uuid} eq '-')) {
           # NOTE: received_uuid is not in @required_keys (needs btrfs-progs >= 4.1 (BTRFS_PROGS_MIN))
           # so we only check it if it's really present
-          ERROR "[send/receive] received_uuid is not set on target: $vol_received->{PRINT}";
+          push @cmd_err, "received_uuid is not set on target: $vol_received->{PRINT}";
           $send_receive_error = 1;
         }
         if($parent && ($detail->{parent_uuid} eq '-')) {
-          ERROR "[send/receive] parent_uuid is not set on target: $vol_received->{PRINT}";
+          push @cmd_err, "parent_uuid is not set on target: $vol_received->{PRINT}";
           $send_receive_error = 1;
         }
         if((not $parent) && ($detail->{parent_uuid} ne '-')) {
-          ERROR "[send/receive] parent_uuid is set on target: $vol_received->{PRINT}";
+          push @cmd_err, "parent_uuid is set on target: $vol_received->{PRINT}";
           $send_receive_error = 1;
         }
       }
@@ -1545,7 +1534,7 @@ sub btrfs_send_receive($$;$$$)
       $is_garbled = ((not $detail->{readonly}) && defined($detail->{received_uuid}) && ($detail->{received_uuid} eq '-'));
     }
     else {
-      $err = "" if($send_receive_error); # ignore $err if send/receive failed
+      push @cmd_err, "failed to check target subvolume: $vol_received->{PRINT}", @stderr;
       $send_receive_error = 1;
     }
   }
@@ -1554,7 +1543,7 @@ sub btrfs_send_receive($$;$$$)
 
   if($send_receive_error) {
     ERROR "Failed to send/receive subvolume: $snapshot->{PRINT} " . ($parent_path ? "[$parent_path]" : "") . " -> $vol_received->{PRINT}";
-    ERROR "... $err" if($err);
+    ERROR map("... $_", @cmd_err);
   }
 
   if($is_garbled) {
@@ -1619,13 +1608,8 @@ sub btrfs_send_to_file($$$;$$)
     rsh => vinfo_rsh($source, disable_compression => $stream_options->{stream_compress}),
     name => "btrfs send",
     stream_options => $stream_options,
-    exitcode_loglevel => "error", # print error message if exitcode != 0
-    catch_stderr => 1, # hack for shell-based run_cmd()
-    filter_stderr => sub {
-      return { error => $_, fatal => 1 } if(s/^ERROR: //); # "fatal" causes run_cmd to return undef
-      return { warn  => $_ } if(s/^WARNING: //);
-      return undef;
-    },
+    filter_stderr => [ \&_btrfs_filter_stderr, sub { $_ = undef if(/^At subvol/) } ],
+    fatal_stderr  => sub { m/^ERROR: /; },
   };
 
   if($compress) {
@@ -1702,12 +1686,18 @@ sub btrfs_send_to_file($$$;$$)
           DEBUG "Generating session key for: $vol_received->{PRINT}";
           my $kdf_backend_name = $encrypt->{kdf_backend};
           $kdf_backend_name =~ s/^.*\///;
+          my $key_target_text = $encrypt->{kdf_keygen_each} ? "\"$vol_received->{PRINT}\"" : "all raw backups";
 
-          print STDOUT "\nGenerate session key for " . ($encrypt->{kdf_keygen_each} ? "\"$vol_received->{PRINT}\"" : "all raw backups") . ":\n";
+          print STDOUT "\nGenerate session key for $key_target_text:\n";
           my $kdf_values = run_cmd(cmd => [ $encrypt->{kdf_backend}, $encrypt->{kdf_keysize} ],
                                    non_destructive => 1,
                                    name => $kdf_backend_name
                                   );
+          unless(defined($kdf_values)) {
+            ERROR "Failed to generate session key for $key_target_text", map("... $_", @stderr);
+            return undef;
+          }
+
           return undef unless(defined($kdf_values));
           foreach(@$kdf_values) {
             chomp;
@@ -1803,8 +1793,13 @@ sub btrfs_send_to_file($$$;$$)
   my $ret;
   $ret = system_write_raw_info($vol_received, \%raw_info);
 
+  my @cmd_err;
   if(defined($ret)) {
     $ret = run_cmd(@cmd_pipe);
+    @cmd_err = @stderr unless(defined($ret)); # save for later
+  }
+  else {
+    push @cmd_err, "failed to write raw .info file: $vol_received->{PATH}.info", @stderr;
   }
 
   if(defined($ret)) {
@@ -1813,9 +1808,10 @@ sub btrfs_send_to_file($$$;$$)
     # redirection as well as "dd" always creates the target file.
     # Note that "split" does not create empty files.
     my $test_postfix = ($split ? ".split_aa" : "");
-    DEBUG "Testing target data file (non-zero size)";
+    my $check_file = "${target_path}/${target_filename}${test_postfix}";
+    DEBUG "Testing target data file (non-zero size): $check_file";
     $ret = run_cmd({
-      cmd  => ['test', '-s', { unsafe => "${target_path}/${target_filename}${test_postfix}" } ],
+      cmd  => ['test', '-s', { unsafe => $check_file } ],
       rsh  => vinfo_rsh($target),
       name => "test",
     });
@@ -1824,10 +1820,14 @@ sub btrfs_send_to_file($$$;$$)
       delete $raw_info{INCOMPLETE};
       $ret = system_write_raw_info($vol_received, \%raw_info);
     }
+    else {
+      push @cmd_err, "failed to check target file (not present or zero length): $check_file";
+    }
   }
   end_transaction("send-to-raw", defined($ret));
   unless(defined($ret)) {
     ERROR "Failed to send btrfs subvolume to raw file: $source->{PRINT} " . ($parent_path ? "[$parent_path]" : "") . " -> $vol_received->{PRINT}";
+    ERROR map("... $_", @cmd_err);
     return undef;
   }
   return 1;
@@ -1841,8 +1841,6 @@ sub system_list_mountinfo($)
   my $ret = run_cmd(cmd => [ qw(cat), $file ],
                     rsh => vinfo_rsh($vol),
                     non_destructive => 1,
-                    exitcode_loglevel => "error", # print error message if exitcode != 0
-                    catch_stderr => 1, # hack for shell-based run_cmd()
                    );
   return undef unless(defined($ret));
 
@@ -5195,11 +5193,11 @@ MAIN:
     # NOTE: ssh://{src,target} uses default config
 
     my $src_vol = vinfo($src_url, $config);
-    unless(vinfo_init_root($src_vol)) { ERROR "Failed to fetch subvolume detail for '$src_vol->{PRINT}'" . ($err ? ": $err" : ""); exit 1; }
+    unless(vinfo_init_root($src_vol)) { ERROR "Failed to fetch subvolume detail for '$src_vol->{PRINT}'", map("... $_", @stderr); exit 1; }
     if($src_vol->{node}{is_root})     { ERROR "Subvolume is btrfs root: $src_vol->{PRINT}"; exit 1; }
 
     my $target_vol = vinfo($target_url, $config);
-    unless(vinfo_init_root($target_vol)) { ERROR "Failed to fetch subvolume detail for '$target_vol->{PRINT}'" . ($err ? ": $err" : ""); exit 1; }
+    unless(vinfo_init_root($target_vol)) { ERROR "Failed to fetch subvolume detail for '$target_vol->{PRINT}'", map("... $_", @stderr); exit 1; }
     if($target_vol->{node}{is_root})     { ERROR "Subvolume is btrfs root: $target_vol->{PRINT}"; exit 1; }
 
     unless(_is_same_fs_tree($src_vol->{node}, $target_vol->{node})) {
@@ -5301,7 +5299,7 @@ MAIN:
         $realpath_cache{$mnt->{mount_point}} = $mnt->{mount_point}; # we know those are real paths, prevents calling readlink in btrfs_mountpoint
         my $vol = vinfo($mnt->{mount_point}, $config);
         unless(vinfo_init_root($vol)) {
-          ERROR "Failed to fetch subvolume detail for: $vol->{PRINT}" . ($err ? ": $err" : "");
+          ERROR "Failed to fetch subvolume detail for: $vol->{PRINT}", map("... $_", @stderr);
           exit 1;
         }
 
@@ -5381,12 +5379,12 @@ MAIN:
 
     my $src_root = vinfo($src_url, $config);
     unless(vinfo_init_root($src_root)) {
-      ERROR "Failed to fetch subvolume detail for '$src_root->{PRINT}'" . ($err ? ": $err" : "");
+      ERROR "Failed to fetch subvolume detail for '$src_root->{PRINT}'", map("... $_", @stderr);
       exit 1;
     }
     my $archive_root = vinfo($archive_url, $config);
     unless($archive_raw ? vinfo_init_raw_root($archive_root) : vinfo_init_root($archive_root)) {
-      ERROR "Failed to fetch " . ($archive_raw ? "raw target metadata" : "subvolume detail") . " for '$archive_root->{PRINT}'" . ($err ? ": $err" : "");
+      ERROR "Failed to fetch " . ($archive_raw ? "raw target metadata" : "subvolume detail") . " for '$archive_root->{PRINT}'", map("... $_", @stderr);
       exit 1;
     }
 
@@ -5421,18 +5419,18 @@ MAIN:
       my $sroot = vinfo($sroot_url, $config_sroot);
       vinfo_assign_config($sroot);
       unless(vinfo_init_root($sroot)) {
-        ABORTED($sroot, "Failed to fetch subvolume detail" . ($err ? ": $err" : ""));
-        WARN "Skipping archive source \"$sroot->{PRINT}\": " . ABORTED_TEXT($sroot);
+        ABORTED($sroot, "Failed to fetch subvolume detail");
+        WARN "Skipping archive source \"$sroot->{PRINT}\": " . ABORTED_TEXT($sroot), map("... $_", @stderr);
         next;
       }
 
       my $droot = vinfo($droot_url, $config_droot);
       vinfo_assign_config($droot);
       unless($archive_raw ? vinfo_init_raw_root($droot) : vinfo_init_root($droot)) {
-        DEBUG "Failed to fetch " . ($archive_raw ? "raw target metadata" : "subvolume detail") . " for '$droot->{PRINT}'" . ($err ? ": $err" : "");
+        DEBUG "Failed to fetch " . ($archive_raw ? "raw target metadata" : "subvolume detail") . " for '$droot->{PRINT}'";
         unless(system_mkdir($droot)) {
           ABORTED($droot, "Failed to create directory: $droot->{PRINT}/");
-          WARN "Skipping archive target \"$droot->{PRINT}\": " . ABORTED_TEXT($droot);
+          WARN "Skipping archive target \"$droot->{PRINT}\": " . ABORTED_TEXT($droot), map("... $_", @stderr);
           next;
         }
         $droot->{SUBDIR_CREATED} = 1;
@@ -5445,8 +5443,8 @@ MAIN:
         else {
           # after directory is created, try to init again
           unless($archive_raw ? vinfo_init_raw_root($droot) : vinfo_init_root($droot)) {
-            ABORTED($droot, "Failed to fetch subvolume detail" . ($err ? ": $err" : ""));
-            WARN "Skipping archive target \"$droot->{PRINT}\": " . ABORTED_TEXT($droot);
+            ABORTED($droot, "Failed to fetch subvolume detail");
+            WARN "Skipping archive target \"$droot->{PRINT}\": " . ABORTED_TEXT($droot), map("... $_", @stderr);
             next;
           }
         }
@@ -5616,8 +5614,8 @@ MAIN:
     next unless(grep defined($_->{GLOB_CONTEXT}), @{$config_vol->{SUBSECTION}});
     my $sroot = vinfo($config_vol->{url}, $config_vol);
     unless(vinfo_init_root($sroot)) {
-      ABORTED($sroot, "Failed to fetch subvolume detail" . ($err ? ": $err" : ""));
-      WARN "Skipping volume \"$sroot->{PRINT}\": " . ABORTED_TEXT($sroot);
+      ABORTED($sroot, "Failed to fetch subvolume detail");
+      WARN "Skipping volume \"$sroot->{PRINT}\": " . ABORTED_TEXT($sroot), map("... $_", @stderr);
       next;
     }
 
@@ -5953,15 +5951,15 @@ MAIN:
   foreach my $sroot (vinfo_subsection($config, 'volume')) {
     DEBUG "Initializing volume section: $sroot->{PRINT}";
     unless(vinfo_init_root($sroot)) {
-      ABORTED($sroot, "Failed to fetch subvolume detail" . ($err ? ": $err" : ""));
-      WARN "Skipping volume \"$sroot->{PRINT}\": " . ABORTED_TEXT($sroot);
+      ABORTED($sroot, "Failed to fetch subvolume detail");
+      WARN "Skipping volume \"$sroot->{PRINT}\": " . ABORTED_TEXT($sroot), map("... $_", @stderr);
       next;
     }
     foreach my $svol (vinfo_subsection($sroot, 'subvolume')) {
       DEBUG "Initializing subvolume section: $svol->{PRINT}";
       unless(vinfo_init_root($svol)) {
-        ABORTED($svol, "Failed to fetch subvolume detail" . ($err ? ": $err" : ""));
-        WARN "Skipping subvolume \"$svol->{PRINT}\": " . ABORTED_TEXT($svol);
+        ABORTED($svol, "Failed to fetch subvolume detail");
+        WARN "Skipping subvolume \"$svol->{PRINT}\": " . ABORTED_TEXT($svol), map("... $_", @stderr);
         next;
       }
       if((not $svol->{node}{uuid}) || ($svol->{node}{uuid} eq '-')) {
@@ -5991,8 +5989,8 @@ MAIN:
 
       my $snaproot = vinfo_snapshot_root($svol);
       unless(vinfo_init_root($snaproot)) {
-        ABORTED($svol, "Failed to fetch subvolume detail for snapshot_dir" . ($err ? ": $err" : ""));
-        WARN "Skipping subvolume \"$svol->{PRINT}\": " . ABORTED_TEXT($svol);
+        ABORTED($svol, "Failed to fetch subvolume detail for snapshot_dir");
+        WARN "Skipping subvolume \"$svol->{PRINT}\": " . ABORTED_TEXT($svol), map("... $_", @stderr);
         next;
       }
       unless(_is_same_fs_tree($snaproot->{node}, $svol->{node})) {
@@ -6018,16 +6016,16 @@ MAIN:
           if($target_type eq "send-receive")
           {
             unless(vinfo_init_root($droot)) {
-              ABORTED($droot, "Failed to fetch subvolume detail" . ($err ? ": $err" : ""));
-              WARN "Skipping target \"$droot->{PRINT}\": " . ABORTED_TEXT($droot);
+              ABORTED($droot, "Failed to fetch subvolume detail");
+              WARN "Skipping target \"$droot->{PRINT}\": " . ABORTED_TEXT($droot), map("... $_", @stderr);
               next;
             }
           }
           elsif($target_type eq "raw")
           {
             unless(vinfo_init_raw_root($droot)) {
-              ABORTED($droot, "Failed to fetch raw target metadata" . ($err ? ": $err" : ""));
-              WARN "Skipping target \"$droot->{PRINT}\": " . ABORTED_TEXT($droot);
+              ABORTED($droot, "Failed to fetch raw target metadata");
+              WARN "Skipping target \"$droot->{PRINT}\": " . ABORTED_TEXT($droot), map("... $_", @stderr);
               next;
             }
           }
@@ -6077,7 +6075,7 @@ MAIN:
     my $url = $subvol_args[0] || die;
     my $vol = vinfo($url, $config);
     unless(vinfo_init_root($vol)) {
-      ERROR "Failed to fetch subvolume detail for: $url" . ($err ? ": $err" : "");
+      ERROR "Failed to fetch subvolume detail for: $url", map("... $_", @stderr);
       exit 1;
     }
     if($vol->{node}{is_root}) {