What --log-file-log-level did you use? I suggest verbose.
If verbose is too much, try Information
What would be helpful (but it’s a lot of steps) is
- Starting with a working backup job
- Turn on
--log-file-log-level(as you have) - experience non-empty blocksets error (well, I hope you don’t, I hope no one does, but if you do)
- perform sql query in database browser
- Find 5 of 10 files “around” where the failing file was
- go back to logfile and search for those files. This is likely from previous runs, not the current that received the error.
- hopefully something in the logfile will be revealing