Thank you so much for your feedback! Actually, I think your solution would work well, but I'll have to check if it can be implemented or not: the more leeway the game gives to the player, the more prone to prompt a bug it is, as you have already seen. That error message you keep encountering means precisely that, that the game system doesn't know what scene it should go to next. It would help me a lot if you could tell me, here or in a PM, what day in the game you find that screen. Right now I can only work on the game on the weekends, so I'll try to fix everything I can right away, before Monday.
I'm glad you are enjoying the story and the characters, despite the game's flaws!