I don't have time now to go through all the files one-by-one, but I was able to copy the save file for my campaign from my mod over to the vanilla game and load it, and it still had the same error at the same time.
Note: This was a few turns into the game (turn 8 I think), so I don't think it is a mp problem, because then shouldn't it have triggered on the first turn (when the modded file would first take effect)? Like on the first turn, I was able to move my spy for all of his mp, without a crash.
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