Post-game Screen not showing up after game

The problem is the post-game stats not appearing. When I finish a game and click continue underneath Victory/Defeat, it appears that I do not actually leave the game. What I mean by this is that the actual game client is still running in the background even though I already left the game. Normally when you click continue, the game will exit and the LoL client will pop back up with the game stats, but that doesn't seem to happen. Unless I go to the task manager and end the LoL game process, I'm still technically in the game. I forgot to delete the process once, and my friends told me that I've been in-game for over 4 hours, even though I went off to do other things. This problem has been happening to me personally around the beginning of the pre-season (2015), but a couple of my friends have said this has been happening to them for years. I've been getting by with just keeping my task manager open to delete the process after every single game, but it still remains extremely annoying.