The reformation should happen sometime between 1417 and 1517. I think the end turn crash indicates that it was going to happen, but something went wrong It can be a missing text or something like that, but I had testet the reformation and it worked... mhhh
Can you upload your savegame?
I will look at the farms and maybe tie the effects to the factions, this should help with the problem.
Edit:
I just checked, your crash seems to be indeed the Reformation. I forgot to activate the random counter so it will happen around 1517 or so.
I will test this out later that day.