Null, lag, you lose, app crashing and closing, opponents chucking long balls that you can't defend against, backpass, scripting that makes you lose against lower rated opponents are the classic problems of this game. Now what caused this sudden rating decrease is: 1) inability to play or do something due to server issues, matches getting nulled because of the same. 2) Same boring events and cheap rewards. 3) you could buy 10k coins and get duplicate iconics. 4) clickbaiting notifications.