Sorry, it's could not be fixed. SIF system is not very good-working, so there is bunch of bugs. And sometimes if game is freezed on save the save slot brocken. It's why you should save often and use both memcard and savestates saves.
It's recomended to keep some backups of your memory cards in case something like this happens, the emulator isnt perfect and it could have trouble like this. I've heard having too many saves for the same game can cause it.