An issue i experienced was the medals given to me in game. Specifically; i got 25 kills and no deaths at all and at the end of the match i did not receive the perfection medal nor untouchable for my kill streak, i did get rampage however. After the match i checked my commendations and nothing had changed.
Another issue is dying so fast in gametypes such as Dominion and BTB from across the map by DMR's. Its pretty frusterating, especially when the Carbine, and BR cant put up a fight with it.
I had this issue, what i did was:
1. Dashboard
2. Went to Account on the farthest right tab
3. Clicked on download history
4. navigated until i found "Armor specialization priority alpha" (something like that)
5. Re downloaded it and went back to halo and the problem was fixed.
Hope this works out for you