Live video not going full screen in Safari

[topipad]

When I play a live stream video in safari and click to go full screen it doesn't, all the Safari menus etc still show.

If I try to mirror my iPad to my Apple TV the TV shows the iPad screen with black pillar box bars either side.

If I play the same live stream on my iPhone Safari it does go full screen and when I mirror to my Apple TV it also goes full screen.

Does anyone know the cause of this and a fix?

Just to be clear this is a legal subscription service for my sports team that plays highlights and also has a live stream TV channel. But I've noticed it with all live streaming, not specifically this one.

Thanks.