Black screen with a white box while watching YouTube videos on fullscreen

What it is fellow Apple Users? I have an issue with my computer and I'm wondering if any of you playas can help me out. So, I've been having this issue on and off with my 15 inch retina MacBook Pro (mid-2015) while I watch YouTube videos on fullscreen on Safari. I never get this issue on chrome and I haven't used firebox so I can't attest for the same issue in that browser. I am wondering if anything knows what this problem is, what causes it, and if there is anything I can do to get it fixed.