Sigh…
Disabling every single plugin on the site and now its working.
Sigh… the wordpress eco-system and tools such as x-theme these really should be at a much reduced cost or include real-time support. It is not stable enough as an ecosystem and the potential for unexplainable error is so huge. Like every time you do anything. The amount of conflicts created when adding anything even simple things like a contact form - which result in catastophic breaks of your website and much hand wringing.
Invaribaly the “solution” is to disable all plugins. But then the system sometimes “works” with such plugins. Many times its an error with the theme itself, or possibly some hosting issue.
The promise of a smoothly running cms and website experience (which is what we pay for) never occurs. Even if it isnt a plugin issue, cornerstone/x-theme itself is guaranteed to hang/fail during a session which only a cahce clear/reboot seems to fix.
anyway - for others who get this issue - this is another “disable all plugins” and this will “solve” your issue, type issue.