Hi @dcheese,
I’ve checked your site and I’m seeing some other javascript errors, but not the one from your screenshot. In either case, this usually happens when a script error occurs in another plugin and it halts the rest of the javascript on the page from running.
Regarding the AbortController error, even though I’m not seeing it, it could happen if a third party script overwrites the version of React bundled with WordPress. Pro (and Cornerstone) uses the WordPress React dependency to display the preview frame. I’ve seen cases where embed codes pull in a script from offsite that loads their own version of React and ends up breaking the live preview.
First I would recommend testing for a plugin conflict by disabling any plugins you have active and seeing if the problem is corrected. Then you can reactivate plugins one at a time to narrow down the source of the problem.
You could also temporarily remove any custom scripts or embed codes you are using. If you find it to be related to one of those, the Raw Content element has a “disable preview” option that can be used to avoid the code running in the preview frame. This helps reduce conflicts while keeping things working as desired on the site front end.