Video stuck in fullscreen mode

Hello,

I have a problem with my Macbook Pro 15" 2015 base model. This happens a lot and I have no idea why. When I try to watch a youtube video (it happened with videos from other websites too) in fullscreen (by tapping on the bottom right icon on the player), the video continues to play well in fullscreen but the player freezes. I cannot tap the controls, audio,move the video, etc. The problem is that my mouse clicks are not recognised by the video player and I cannot exit it. It does not happen all the time, maybe in about 35% of cases. (The green button from Safari in the top left corner would not close the window as well)

In order to exit the full screen video, I used to go to the previous Desktop and force quit Safari. Now I have noticed that tapping "Show all Windows" would solve the problem, but it is really annoying. Also, it is not only present in Safari, it happened too in Chrome.

*After tapping Show all Windows and getting back to the youtube video page, where I left, the youtube search bar somehow disappears, as well as the top part. The top of the page gets to be aprox the top line of the video player.