Has anyone else seen this problem?
The first tab on my form is hidden (it contains a web resource). If I use the navigator sidebar to move to a related page, then use the tabs at the top of the page (to the right of File) to move back to the main form, the tab which is supposed to be hidden becomes visible.
I'm aware that sometimes CRM makes tabs or sections visible if they contain the only editable field on the form, but that's not what's happening here. And it only seems to occur for a hidden tab which is the first tab on the form.