Just a note, it appears to be directly linked to saved games. I can create new games (using the exact same mods) but cannot load some games (crash during loading screen). It generally appears to happen after a few seasons so it may have something to do with the state of the game when it is saved, but I cannot think of a consistent variable, i.e. it isn't only after windmills or some sort of item is obtained.
Also, I can usually hear an audible click right before games are successfully loaded, which I hear when the saved games crash which makes me think the error occurs late in the loading process.