I have to keep changing my submit preference (for live games) back to double-click. It’s hard to say how often it reverts, but it’s pretty frequent; weekly if not daily.
I frequently clear my browser history (Firefox), but not cache or logins. Other settings such as sound preferences seem to be unaffected.
It’s the cookies you got to hold on to me thinks… Try not clearing history for a couple weeks. Make all trips to the Hub in private browsing mode 
This setting should be saved in the “local storage” of the browser. If you delete “offline website data”, this will be cleared.
You can configure Firefox to automatically delete this data upon exiting and then add sites to be exempt from this. See for example the first response here,
As far as I can tell, my setup does keep cookies, even when Firefox is closed or other history elements are cleared. The issue also only seems to affect this one setting, and not other settings I’ve seen default in the past when clearing cookies or longing out, such as sound settings or dark mode.