Video display half of the screen when size reduce and maximize

After installing the player and leaving everything in the default setting whenever I view youtube videos from mobile phone the videos image move to the top of the screen and the lower half is blank. This also happens when I resize my browser and when I click on the fullscreen button. The attach image shows whats going on.

I get the same issue even when I click on fit scale and also when I enter custom height and width for the video.

Screen-Shot-2018-06-02-at-9.11.19-AM