I ve had it happen twice. Once was odd. The second time it cost me the game. (Minor problems in the grand scheme of life.)
This is an exceptionally straight forward app that they just can't seem to get right.
Next call is to Apple for refund.
Same thing happened to me, twice. Was going to end the game with 70+ armies in one country on progressive card change and when I attached the losing player game disconnected. It reconnected me right back in and when I came back in both times the other player had my 70+ armies.
Yes, this is rampant, and horrible.