Halo 4 Challenges and game glitches suck

I pre orderdthis game and they all gave to like a 9.75 when they rated it. BUT they do not tell you that the challenges they put there to earn xp do not always register you have completed them. And online a LOT of the time you watch the kill cam to see how you died the guy is not even looking at you and he is shootong you thru a solid object still not looking at you. I know lag has a lot to do with that but it happens WAY too much for just that. PLEASE fix these problems, or next week I will be trading it towards Hitman.