Unwanted controls on iPhone while watching TV

#1

While watching the debate tonight on my iPhone Xʀ, control bars kept appearing at the top and bottom of the display for no apparent reason. I wasn’t even touching the phone. How can I prevent that? I haven’t seen that behavior on my iPad. They would go away if I touched the screen, but only temporarily.

#2

We haven’t noticed this here, but we’ll see if we can reproduce this behaviour. Has anyone else seen this?