YouTube control menu doesn't disappear!

[ymaz108]

I recently got Google Pixel 2 XL with now Android 8.1.0.

When I played YouTube videos, I noticed the control menu (rewind/pause/forward) on the screen DON'T DISAPPEAR at all throughout the entire playback...!

Does anyone know how to get lid of it?

Also, that makes the video image dark, so I can't watch well...

I researched online and tried to implement those methods, but none work...(┯_┯)

I hope there is a way...

 

[ymaz108]

UPDATE:
I still do not know what happened, but it eventually DISAPPEARED...