Weird fullscreen animation on mac

So on my macbook when I enable fullscreen the anmation is super weird. first it stretches the video to the top and then just expands to the whole screen, when I go out of fullscreen is stretches to the bottom and then goes out off fullscreen. for example on safari it just expands the video until it takes up the whole screen. I have gone in about:config and disabled the fullscreen animation but that did nothing.