So I created a working copy, created a copy of the standard page template called “Standard_With_Keep_Alive”. I assigned that page template across all pages that needed it in the working copy.
I merged the working copy into main, and then the whole application blew up. The MAIN copy did not have this new page template I created. All pages were uneditable, the Editor just said “This page has no page template”, and I couldnt do anything such as manually reassign the standard template back.
I tried manually creating a page template with the same name in the MAIN copy, in case that sprung everything back into life, but not luck. By some miracle I had taken a back up as part of the merge, so I had to restore all apps to before the merge, but then manually had to redo all the work from the working copy.
Why arent templates you create in a working copy, merged along with everything else, this was a disaster, breaking 13 production applications.