Thanks for asking and sharing the video screencast.
Just to let you know that Cornerstone is a required plugin to smoothly run X Theme. As you are using Cornerstone element inside blog post or let's say if you choose not to use Cornerstone, it's a required plugin.
Please try out following solutions for the problems you are facing with Cornerstone:
- Increase the PHP Memory Limit of your server. Click here for more detailed information and how to increase the PHP memory limit.
- Make sure that you're running at least PHP v5.6.x or later to avoid any WordPress related incompatibility issues. If you're not sure what your server configurations and settings are, install a plugin like WP-Serverinfo (https://wordpress.org/plugins/wp-serverinfo/) and check your server info by head over to Dashboard -> WP Serverinfo area.
- If you're using a CDN, please clear the CDN's cache and disable optimization services.
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.