Another firefox issue.
And it is not just UBB it seems to be any type of form submitter it just hangs or does not display the next step page so I switch to edge when it happens.
In fact I can't login to my bank or insurance site with firefox anymore.
++++1
I've been having the same issues (with Firefox) in Joomla.
Not just Firefox though, some oddities occur with whatever the new version of IE is called.
Chrome seems to be okay, but for best results, I have to use Opera(!)
