Enough MMR but doesn't up my league

Hello everyone,
I have recently seen a bug in the game.
I am right now diamond 1 and I can not up master, I reached 4080 MMR (the requirement to up master in 2v2).
but also with another friend and still the same problem.
It’s just not really rewarding to do his best to up master and still be stuck in the diamond league when we see everyday lower MMR team in master league.
Is this bug gonna be fixed soon? are you currently knowing this problem?
Thank you to have read my post!
I am looking forward to hearing from you.