Client Randomly Closes

I've tested League of Legends on multiple machines. (Not at the same time with the same account.) For whatever reason, within the first ten minutes of the game, usually around 4 minutes but sometimes around 7, my game will minimize for no reason. I could be at base, or escaping or looking to make a play and in the middle of doing whatever it is I'm trying to do the game would just minimize at random. Has anyone else experienced this issue? I've done a lot of troubleshooting and double checked my hotkeys, it's not human error. My machines are fine.