How is this even possible ? Oddball winning glitch

Seriously how unfair is this ? I am diamond 5, won a very hard oddball game and finished with 1:29 with the skull, 26 frags and 19 deaths and I am deranking back to diamond 4! How frustrating is this thing ? It just make me want to quit ! 343i really need to fix this !

It happened again OMG ! Just another win and derank again!!! I am hating this game for real at the moment!!