[GAMEPLAY][CRASH| Settings change then crash

I was playing Kindred and all appeared to be going normally. Since pre-season has started, the gameplay has been a little grainy and not as smooth as the regular season. About 10 minutes into the game, the sound randomly turned off without any changes to the settings (i think). Then, the FPS began decreasing rapidly to about 09 FPS.

1. Sound turns off at around 10:00 min (estimate).
2. FPS begins to decrease gradually thereafter.
3. Checked sound settings, all appears to be normal.
4. Attempt to disable all sound to reset the settings in-game.
5. Game begins to not respond. Unable to minimize or use CTRL+ALT+DEL to switch programs.
6. Able to close LoL through the sign off function in Windows (which prompted if you are certain you want to log off)
7. Reconnect to LoL and game was in session.
8. Sound continued to be off without the "disable all sound" command in settings.
9. FPS returns to normal (grainy) gameplay.

I'm not sure whether its the implementation of the pre-season, my computer, or some other factor. The sound during the lobby after the game was playing and appears to be normal. I only experienced issues with that game regarding the sound and decrease FPS, though the FPS has been lower for all pre-season games.

My team also wanted to report me for AFK. They were being mean after I AFK because of the crash, though i was telling them the sound and FPS issues prior to my game crashing.

Thanks!