Connecting to Game but being unable to use mouse or keyboard after connecting to game

I've looked through previous posts and have been unable to find one that refers to the problem I have encountered.

So this is a problem I have encountered twice already. It occurs ingame. The first time I encountered it was during a game. It was relatively late, and suddenly my mouse had gone from being the normal LoL style mouse to the normal mouse as well as being unresponsive in game. Next to this my keyboard was also unreponsive. In other words I was stuck. Unable to move or cast abilities and not able to leave the game or enter options. Now while this may have occurred during a game, which was frustrating enough, it happened again at the start of another game. I was unable to do anything and had to force shut down my PC as there was no way of getting out.

I know that the discord overlay does conflict with the game and does cause cases where the keyboard is unresponsive and I encountered this bug myself and since have the discord overlay switched off. But even so, the bug caused by discord didn't lead to utter unresponsiveness. If someone knows what causes this/ how to fix it, feel free to share as this is utterly frustrating to be stuck and to get an AFK warning for something seemingly out of ones control.