Got to love losing a match before Riots client locks on the load screen and you have to hard reboot

I find it helps to reset the client before every ranked game. I've been doing so for the past few days and haven't had this occur again, though I may just be lucky.

Read this post i made. It will help you a ton.

https://boards.na.leagueoflegends.com/en/c/general-discussion/fXcp9Ewx-a-guide-for-when-lol-is-crashing-at-loading-screen-and-wont-start-computer-freezing