Once a jam is submitted, it can be modified any time BEFORE the end date of the jam.  Once the end date hits, the submission cannot be touched for the next month, to give us and the community a chance to look at and play through the games.  That means any mistakes not fixed before the final jam day must remain in the game until the end of December.  Then, you are free to update.  It is part of the challenge of the jam, and we keep the rule in place so that games don't continue to update and change after the Jam closes.  Giving everyone an equal opportunity to show off what they can accomplish in a month.