pfSense

Disclaimer - this happened, but I'm not sure what caused it, or what exactly fixed it. Raising as issue in case it happens to others or someone can make sense of what I saw, and what might have fixed it.

I have just installed a new browser on my desktop (a well-known Firefox fork, Pale Moon). I logged into my router (2.3 snapshot). The usual "top bar" menu had been replaced unexpectedly by a drop-down top menu (small-device style). I found the "system general setup" menu and the only relevant option relating to the top menu seemed to be fixed/scroll, so I switched to fixed, found that this (of course) prevented seeing the bottom items in the top-level menus, and fumbled around on redmine for a bit looking for hints, then unswitched it back to "scroll". At which point I noticed the router's top bar of menus had reappeared as it usually appears, and it's now fine.

I can't find what happened to trigger it into small-device layout when it's never been that before, nor what happened to switch it back. Any ideas in case it happens again, or happens to others? I didn't modify any broweser settings or user agent, and the browser window was a large one.