Is this the initial backup? If that can happen, it’s the most interesting and potentially debuggable, provided Creating a bug report button is pushed, and result made available. Otherwise there’s nothing to examine.
Making a manual backup copy of the database would be good, as the bug report lacks the original names. Some interesting find in the sanitized version might need you to get file names using directions how to do.
Thank you.
Backup started failing “non-empty blocksets with no associated blocks” was a recent beg for information.
Is that at the end of the backup or at start of the next? If at end, it’s the “nice” case, and info is most useful.
If it’s at the start, then you would have some prior backup logs, so please post the logs leading up to issue.