If there's a full screen error message in the game itself, can you tell me what the error message(s) say? Just the stuff under "While running game code". That'll help me see what's up. If it's some sort of PC pop-up I'll be curious to know what it says as well...
If you haven't already, you could also try doing a speedrun from the beginning using the skip feature, which usually fixes it if it's some sort of choice flag issue. Sometimes the saves don't play nicely with new updates, which unfortunately can happen with an in-development game like this.