Cannot change mastery

Whenever i get into a rank game, I cannot change my mastery. For example, previous game I go Annie and the next game, I play lee sin and I change my mastery. When I go into the game, I have Annie Mastery. After the lee sin game, I go into another ranked game. When i go into the lobby, my mastery is set at Annie mastery. The first time it happened, I thought, i guess i didnt select the correct one last game. But it happened throughout 5 games. Plz fix this bug. This bug is making me edit Annie mastery before every ranked game because i cant change to other 19 masteries.