Till now, my colleagues tried to pinpoint the issue and ruled out many possible cases, that is why we need to double check the case for that specific page you are talking about.
I followed the steps below to add a new test page and use the template functionality of the Cornerstone to duplicate the page:
After that, add a test page and go to the Cornerstone and use the same template functionality, but this time to load the previously added template to the new one.
Then check the case and see if you still have the problem. If yes try then try to delete the sections one by one on that test page, save and go out of the Cornerstone and get back to check.
This will show if the problem exists in a specific section or not. If yes then you need to investigate further to find which element or code is causing the issue.
I already added the Test Page and added the Test Page template, you just need to load the template there and do the test mentioned above.
Regarding the necessity of doing changes on the sales page, I want to offer an alternative way to edit your page at the moment so it will not hurt your business. Kindly use the Skeleton mode at the moment to do your changes:
As a test, I added one additional
! to your headline and it worked ok:
So you can use the Skeleton mode to do the quick changes you need till you find out the cause of the preview fail.
Thank you for your cooperation.