[client] [crash] Constant crashing of PVP.net Client (doesn't affect games I'm currently in)

The game's client is CONSTANTLY crashing on me. It often happens when I'm in the middle of the game. The game will continue playing just fine, but I don't get to see end-game stats and I have to restart League. Annoying, but bearable.

But now it's killing itself when I try to queue up, causing me to get abandonment punishments, which is unacceptable because I'M NOT THE ONE DOING IT.

I've tried repairing. I've tried uninstalling/reinstalling completely (config files and all). None of it works.

I'm using Windows 10 Insider Preview, which is probably a part of it but nothing else I use has issues like this.