Ranking (leveling up) system not working well.

After the latest update I have run into an issue with the leveling up system. It started when I reached Diamond 6 in Ranked 3v3 X. The first match I win every night gives me a fair 20% or so. Then every single match I win after that gives me like a 4%, 2%, 6%, and it takes forever to level up. I won 12 matches in a row, made it from 16% to 96% last night. Then I lose only one match and it takes me down to 36% again.
This has happened to me twice already in the last week and it’s becoming a bit frustrating. The first time it happened it deducted so much that from Diamond 6, it brought me down to halfway Diamond 5.
Is this supposed to happen or there is a bug or something causing all this problem?
Platform: Xbox One