There is a report above (and others elsewhere) that Repair worked, but some other reports that it did not. Both Repair and Recreate are being redesigned and rewritten, but I don’t know timetables or functionality.
Fatal error: Detected non-empty blocksets with no associated blocks gave some more technical ideas… Basically, if you can find a pathname that’s causing trouble, maybe you can just purge the problem away, depending on how valuable the backup of the particular file is, weighed against alternatives like Recreate.
If nothing else, would you be willing to post a database bug report as mentioned there? Nobody ever has.
Also, can you look at the job log just before the failure to look for “DeleteResults” and “CompactResults” looking like they did anything on that run? Also, look for any other unusual warnings or errors, or just post the whole thing if there’s nothing sensitive in the messages. Put three tildes above and below to format it.