I think I've spotted a potential bug that I posted on the forums about here. @culturedleftfoot also tested this out and found the same issue. It seems that there is either an issue with using edited databases (I'm using TheFMEditor's tier 10 England database) or that, in general, a player on a non-contract or amateur contract can't have there contract changed and an expiration date assigned to it.   See below my initial post in the forum.