Masteries bug in new client

When I access the masteries page and make changes, they reset back after I exit the respective mastery page. This happens every time, whether I'm in champ select, or just in the client menu. Once I was playing Alistar support (on another account) and I changed the keystone from Grasp of the Undyeing to Courage of Colossus, but after I exited the mastery page and the game started, I still had Grasp of the Undieing. What's interesting is that I tried something similar later on, but this time I DID NOT CLOSE the mastery page and waited for the game to start. The changes applied in that case.

If this issue has been reported already, please leave me a link.

Thank you