Navigation bar not hidden when watching video

What version of Android? What version of Firefox? Link to replicate the issue would be helpful. I'm looking at a video on Rumble and not having the same issue on Xperia XZ3 running Android 10. see screenshot

Here's a link to the video. https://rumble.com/v5hx2fx-australia-letter-stop-mrna-vaccines-now.html?utm_source=newsletter&utm_medium=email&utm_campaign=Dr.%20John%20Campbell

Android version 11. Firefox version 131.0.3

This problem happens with every video. If you need the link: https://youtu.be/smmu6imXsVY

When I try it on another device, there is no problem, but mine has a problem.

I see the issue while using 480p, but when I went up to 1080, I only saw black bars on both sides. Why even bother with watching in the browser when the app is far better and easier to navigate??? It's so hit or miss, I do see the full-screen option in the bottom right corner.

I was able to get it while 480 and the full-screen option is showing in the bottom right corner. Definitely not worth the effort. 😕😕😕