Backup fails because of a file that is not even into the source directory to be backed up `sync warning: some files vanished before they could be transferred (code 24)`

I am trying to backup the `/User/user01/Library` using `rsync` (via the linux-timemachine wrapper `https://github.com/cytopia/linux-timemachine`) to an external hard drive `Volumes/name_of_backup` logged in as `user01`. During the backup I get the following error message
```
rsync warning: some files vanished before they could be transferred (code 24) at /System/Volumes/Data/SWE/macOS/BuildRoots/220e8a1b79/Library/Caches/com.apple.xbs/Sources/rsync/rsync-55/rsync/main.c(996) [sender=2.6.9]
```
What I don't understand is that the file `/System/Volumes/Data/SWE/macOS/BuildRoots/220e8a1b79/Library/Caches/com.apple.xbs/Sources/rsync/rsync-55/rsync/main.c` is not even located in the directory that I am trying to backup (namely `/User/user01/Library`). So why does this error appears? And most importantly how can I get rid of the problem?

No repository file or test is named. Start by reading the linux-timemachine wrapper and tracing the rsync invocation that produces code 24, then determine why the reported macOS rsync source path appears in the warning. Done means documenting the cause and a verified way to avoid or handle the backup failure.

Written by the indexing model from the issue text.