Issue with YouTube fullscreen

I have noticed for a little time now that every video I click on to go fullscreen, the screen itself goes weird on me. It becomes shifted diagonally and displays the video screen twice. I have no idea how to fix this issue, or if anyone else is even having this issue with YouTube. I’ve tried turning off Shields and that doesn’t work. I’ve tried tweaking in the window tab of the browser, but that doesn’t to be doing anything either. Help?