After reporting an issue with the extension, the developer fixed it promptly. Updated rating accordingly.

It works well on the latest version of Firefox.

I've been looking for one for mobile, and found yours thanks man.

I have also added the "YouTube uninterrupted" at the same time as "play YouTube in background" from this same developer group. I cannot tell if it is doing it's job or not. However have using for a couple of hours without any issues/pauses--which is exactly what it should be doing! So I believe both extensions are a win.