Found the problem. Go in adjacencies.csv and, in complete defiance of what it says, manually remove this :
62;62;portage;1;-1;-1;-1;-1;It will stop working if you remove this
This line was added because the game doesn't draw straits unless there is also at least a portage in the file. Turns out it just crashes if there is a portage and no straits...
Thank you very much! I've been breaking my head over what I've been doing wrong for a couple of days now. This would likely be one of the last things I would've expected! I do have a few more, less pressing, questions.
1. Is there an easy way to make impassable mountains? I haven't been working with these yet but my current assumption is to use the wasteland thing with a little bit of hands on work.
2. Is there a way for the game to randomize characters for provinces on its own or do characters really need to be hardcoded for each province?
In any case, thank you very much and keep up the good work! This program really makes these kinds of projects much easier!