Desync error?

[[417] senorhelios]

Hi, sorry if I'm messing up the posting etiquette, haven't been on here before. I'm playing the co-op campaign in the DLC with a friend and keep getting a desync error every time I try to enter a turn. This started happening on turn four of the game, has never appened before, and wont' stop popping up. I tried scanning the game files' integrity after doing some google searching but that didn't help. Also tried putting in different commands, also to no avail. Any advice? Thanks