Black glitch flickering bug

First link happened while I was scrolling through my friends list, but has been happening since I installed the alpha client. Randomly, whether I'm moving the mouse or not.

https://gyazo.com/e65d499ccb4bc4a58a356f90fa20fa20 trying to make a game makes it worse but it always replicates like this.

I've tried repairing the client, didn't work. Tried changing the size, didn't work. Even uninstalled and reinstalled league and still have this glitchy effect. Makes it very hard to do anything, and I haven't found anyone else with this problem. I sent in a support ticket and was told to just reinstall again but if it didn't work the first time it's not going to work the second..

Any help/ideas would be appreciated!