I've been playing the Multiplayer Campaign recently, and both me and my campaign partner suffer desynchs in EVERY single battle we try to play; however, naval battles and normal multiplayer battles work perfectly fine.
Any ideas as to why this is? We've played one Multiplayer Campaign naval battle together, which worked fine. We played about 3-4 normal multiplayer battles (with other players, too) which worked perfectly fine.
We found that my own autosave for the Multiplayer Campaign was (very slightly) smaller in size, so i tried sending him a copy of my own file -- that didn't work either. Neither the European nor Spanish Multiplayer Campaign works for us.