I played a game of Warzone last night, my second one.
Our team were terrible (including me), and we lost badly, so when it came to the exit screen I tried to get out of matchmaking. This didn’t seem to work very well, and with about 5 seconds to spare I managed to quit the group. However, when I looked at my stats afterwards it said I’d only played one game of Warzone and nothing from that game seems to have registered.
I used a Legendary XP Booster on that game too - Looking at my REQs I still seem to have that, so at least that’s something. Why did it not record the game?