Hello, I also had a reproducible failure on a full backup of a debian 11 pc, which worked with rsync 3.2.2 but failed with rsync 3.3.3.At some point during the backup file contents ended up the the backuppc transfer log and either the backup stalled or got so slow that it never finished.
I stayed with rsync 3.2.2 until recently I stumbled upon https://github.com/backuppc/backuppc/issues/369#issuecomment-692431546. The suggested solution of adding the argument --no-msgs2stderr to rsync fixed the issue for me. Unfortunately, this argument is unknown in older versions of rsync (e.g. in version 3.1.3 included in debian 10), so it has to be added to the configuration depending on the version of rsync on the pc to be backed up. I am unsure whether I really had the same issue as originally posted but I observed it with the same versions and wanted to share this information hoping it helps someone. Bastian
