Unable to rank up in Slayer even though I win

Can anybody tell me what is going on with Slayers ranking system? All the other ones for me are working fine. No matter how many games I win I can’t rank up, even a little bit. But every time I lose, I go down in rank. It’s been going on now for over a month. I’ve lost my onyx because of it and pretty soon will be a diamond 4.

It’s intentional. It’s the new way that CSR works. It’s all explained here.

The quick and dirty explanation is that your Slayer rank is too high compared to your actual skill in Slayer.