Its been pretty frequent, and then not, and we cannot pin down a cause on what is doing it, 2 human and 3 ai players.

I'm experiencing the same problem.
2 Human Players
6 AI Players

Turn 24 I have a fight with Vodyani, but the fighting never starts when you click to start and never resolves, therefore I'm not able to end my turn. (Saving option also stops working)
If I choose to end the turn without the fight and going to turn 25 the game syncs again, but than if I choose to fight there's the same glitch, the fight wont resolve. (Saving option stops working)

If I choose to end turn 25 without a fight again, from there on the game keeps on a permanent de-sync (Saving option stops working).

We've tried reloading the game many times, but since this first fight with the Vodyani started, the fights started to bug (not resolve) or the next turn becomes de-sync no matter what.