Youtube not going full screen?

[l4ke]

Never seen this before, for some reason when I go full screen on youtube, in Safari I get this.

Here's my specs & setup

GA Z68x D3 B3 (UEFI BIOS)
Geforce 670

El Capitan 10.11.2 with Clover.

Any suggestions what the cause may be?

 

[l4ke]

Is this likely to be a graphics issue? the youtube GUI looks fine in full screen, just the video itself not filling up.

 

[arrivo]

https://productforums.google.com/forum/#!topic/youtube/wKnIFyuqhUk

 > System Preferences > General > Show scroll bars

I change this setting to > When scrolling. And now Youtube video going full screen.