Can any playtesters look at this?

[Edi]

Yes. The first time a single corrupt/out-of-bounds/incorrect item is accessed, the whole shebang goes tits-up. You need to remove the problem sprite altogether and try without it. If the same problem persists after that, it needs more investigating.

Mind you, I'm just conjecturing based on how map files behave. What with the 563 sites (1-563), the game will behave normally as long as you stay in provinces with correct assignment and don't access the nation overview. But as soon as you try to enter a province that has #feature 564+ assigned in the map file, or you press F1 (which accesses the province for site reference) you get the fatal error.

Since mod files, just like map files, are text based sequential command lists where the commands are executed in order, it logically follows that the first instance of accessing an entity supposedly created by an invalid command kills the process dead.

Edi