Update: Right now, the game is madly broken when you load your save, even with the engine patch that came out today. It's an engine issue, nothing I can really do on my end except providing as much details as I can to the engine team (which are extremly talented and responsive). I'm preparing everything they may need right now so that hopefully they can fix it for their next patch release that should be out next week.
In the meantime I'll try to find workaround, and consider the possibility of releasing the update by completely removing the save/load feature (for the whole game. No matter when you load your save, whether it's in the convention or in chapter 1, it will break everything at the convention). It would really annoy me because a new player would have to play the game in one go, otherwise they would have to start over every time (or at least start over from the starting points that I can include), which is really annoying. But It's still a temporary solution, let me know what you think about it.