Your rank system has a huge flaw
Your ranking system has a huge flaw because of the random factor in promos;
Let's say two players have played 3,000 games:
Player A has won 2,500 games, but is diamond,
Player B has won 2,000 games, but is plat;
The difference is one got luckier during promos;
There are people who afk or feed on purpose in rank, and until this is addressed you should change how promos work and how mmr works;
Update your database, tables, and more;