So this has been happening to me for a few weeks now.
Every end of game at the win/defeat screen, whenever I click on the Continue button, the game just freezes and stays like that, usually between 30 seconds to a full minute. If I force close it through task manager then it closes and the post-game lobby comes up with no problems.
I tried going into custom games, and any time I exit the custom game, this happens also. It just freezes for a while after I click Exit.
Also, another problem occurred at the same time, so I'm guessing it kind of is connected. Sometimes when a game starts after champion select, the game does not open, but the icon of the game on the task bar appears, however if I click it nothing happens. Whenever I force close that, the client would let me press the Reconnect button, and then finally the game loads up.
I've tried a full repair, and I re-downloaded the game to no avail.
Please let me know if anyone has ever encountered an issue like that before, and if I can do something to fix it.