Chests and keys!

Hello! So i have been getting exclusively keys and no chests ,at all, in my games even though i have been scoring an S for 3 games in a row! This has been going on for about a month and a half, or so . Also, i noticed that the available chests have been full for about 2 weeks and still, i havent got any chests out of my games with S score, so that cant be the reason. I would really appreciate if someone could solve the mystery and clearify what is going on, because either i am doing something wrong or my client is bugged i suppose.