[CRASH] A critical error has occurred ... (happens randomly)

Hello,

I have a problem that is happening a lot the last 2 weeks. Randomly, a game doesn't want to start. It just mentions that a critical error has occured. And the game refuses to start. Some days this doesn't happen. Other days it happens after 1 game. It always happens after the chamption selection and when the game is about to start. Next I cannot start the game whatever I try. And now Leaverbuster has been activated... While this is totally out of my control :(

Best regards, Niedle