I think in keeping with the spirit of the this jam (and game jams in general), when the deadline hits that's the final version of your game, whether its completed or not, buggy or not. Our game had a pretty serious game-breaking issue we found after the deadline as well but we just left a note telling the players how to avoid triggering the bug. That's probably the best approach.
Editing the game page (description, theme, etc) is completely fine and pretty common.