Happens on the latest 2.3.2 also. In fact, just happened to me.
I suspect it's this elusive bug: https://redmine.pfsense.org/issues/6406
I tried restarting the webconfigurator but it did nothing, never tried the other option as the box is not yet live, just rebooted.
Apparently it's more likely to happen if you leave the web page up for a period of time.
Thankfully it doesn't affect SSH, and it doesn't affect functionality, so it's an annoyance rather than a bona fide forest fire emergency.