Control Center appears over YouTube video in Landscape

[Plett]

Hello all, I am having the issue below. When I rotate my phone for landscape in YouTube part of the control center suddenly appears. What do you think is causing this?
FWIW iphone 12pro Max iOS 14.3

 

[camilasaunder89]

You should close all the apps in the background and then again launch the same thing.

 

[Plett]

Thanks for the tip. I have the problem corrected but restarting my phone to watch a video speaks to something else.
My question was what do you think is causing this?