Hey Rob,
Does the issue only happen when you edit text or the preview doesn’t really work even adding an element to the page? There is a previous bug I see in the Changelog related to this so I’m wondering if you’ve not updated to the latest version of X/Cornerstone or Pro yet.

Please also do or confirm that you have done all of the troubleshooting steps listed here https://theme.co/docs/common-issues
Only if none of the common solutions help, please give us the following information in a Secure Note. Just note that we will deactivate plugins and might do some edits in your site so if that’s not allowed, please copy your live site to a staging server.
- Staging WordPress Login URL
- Admin username and password
- Staging FTP or cPanel access
You can find the Secure Note button at the bottom of your posts.
Thanks.