MPC Turn Time problem

I have played many mpc's before but in a recent one with a friend we get past a few turns fine then we have a problem where the turns go out of sequence. For example, he will finish his turn and for him it will move on to my turn but for me it still says its his turn and vice versa and it will often just get stuck. We have to restart then it works for a few more turns just fine and then the problem comes back. Any ideas?

This seems to happen after some diplomacy has been done by either player.