Thank you for reaching out to us. I checked your setup and I see you're using an outdated versions of X and Cornerstone. Please update X and Cornerstone to the latest versions as many bugs have been addressed in the latest releases. I also noticed the content in your site is being served by the cache, after doing the updates, always remember to clear all caches (if you are using WP Rocket, WP SuperCache or W3 Total Cache) when updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.
If this doesn't work then please check for the following:
Ensure everything is up to date according to our version compatibility list at https://theme.co/apex/forum/t/troubleshooting-version-compatibility/195. Please follow the best practices when updating your theme and plugins. See https://theme.co/apex/forum/t/setup-updating-your-themes-and-plugins/62 for more details.
Clear all caches including browser cache then deactivate your caching plugin and other optimization plugins.
If you're using a CDN, please clear the CDN's cache and disable optimization services.
Test for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
If you still have problems kindly get back to us with the result of the steps above and URL/User/Pass of your WordPress dashboard using the Secure Note functionality of the post to follow up the case.