Try going to my games and apps→halo wars 2→press start→manage game→on the left side of the screen you’ll see a menu, go down to where it says saved data→delete both the reserved space and your accounts saved data
It stopped me from getting a network errors every game, and was alot more convient then having to redownloading the whole thing.
However, it did mess with my service record. It lowered my rank and says I’ve only played 7 hours, but I’m actually able to play the game now. (My rank was set back to the correct rank, thanks 343 if you did that!)