I have this as a statement in my Playstore review, and Mozilla asked me to put it here as a question! But it really is NOT a question and they should have requested it as feedback instead. But I'll expand on it a bit here anyway. The problem involves keeping tabs open all the time. They should not lose their qualities but they do when you leave and then return latet to such a tab when it comes to Desktop Site selection. The flag still shows it as enabled but in actuality when you examine the page itself you find that it no longer behaves like it, and it won't even let you disable and then re-enable it to fix it! It just ignores your presses at that point! It's definitely a bug and it wasn't there earlier at some point although I'm not sure when it stopped working and might have even been with different Android versions being that I had only recently started using it on Android 11. But at some point in earlier Android versions it definitely had worked and the tabs we're also rearrangeable back then as well. The bottom line is that the problem isn't hard to reproduce...it's there CONSTANTLY and you just need to keep your tabs open all the time and try keeping them as desktop selected for them while working on other apps so that it temporarily dies in the background and then returning back and then you'll see right away that it has this problem.  :)