Multiplayer game rollback after skipped turns and kick

[Dicul]

While playing a multuplayer game in AoG, my opponent sometimes takes too long to make their move, so, not wanting to wait, I skipped their turn. The next day the game had rolled back and no turn had been skipped. Not a big issue, but weird.

Recently my opponent didn't take any turns for several days so I thought they had given up, and eventually decided to kick them from the game. I even played a few turns against the AI replacement after this. The next day my opponent was back in the game and the game had been rolled back quite a number of turns. I don't even recognize the game state at this point.

So what's going on?