There is no sure-fire fix procedure that I know of, but you will be able to do a safe trial by doing a manual rename of database (basically like a delete where you can undelete it later if you want to), then a Repair.
If you like, before that, you can run a database bug report to post by link. Maybe it will shed some light…
Posting your last job logs before backup broke would be an easier way for people to maybe spot a clue.
If you personally have any clues on how it came to break, please supply. This would be helpful to the fix.