champion mastery

i am so livid right now ive been trying to get an S on morgana so i can get the mastery tokens but nothing works, even though i get good scores the last game i played with her i got 21 kills 5 deaths and 10 assist and i only got an A+ the last time i got a token for morgana i got a way worst score than this one i got 19 kills 8 deaths and 18 assist and we lost the game and i still got an S + on it. PLZ ether take the mastery system off or fix it because it feels like all the hard work i just did was for nothing