Crashes and unable to rejoin game

The new map ran fine originally on my computer on max settings. I have a very good pc, but since it went into main ques I crash randomly during the games. Today it happened during a teamfight and when I tried to reconnect the client said the game you are trying to reconnect to has already ended. It hadn't. I had friends in the game, and had to sit at the main menu and listen to them loose while I relaunched several times all to the basic client, with no option to rejoin my game. I tried to start other ques and it would let into the match finder, but never actually found a game. I have never had any performance issues with league until patch 4.20. Any assistance would be great.