I've done that before. Wasn't my problem this time (I think it was windows related shenanigans), but if you have a back up save it is definitely possible to have the wrong one in an editor and be mystified when all the changes you've made don't seem to be fixing up the first time it happens. (And very annoying when you have to go back and re-edit the later save that was supposed to be worked on.)
I'm guessing you can update if it's to fix a bug that can prevent you from finishing the game due to this:
2. Less in the case you have a game breaking bug, in that case you are allowed to fix the bug to guarantee players can complete your game.