Thanks for asking.
Could you please try following the guidelines below and see if that helps.
- If you're using a caching plugin, make sure to purge all server cache and disable it until you do the testing.
- Make sure that you're running PHP v7 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.
- Check your
PHP Max Execution Time and set it for 300 for optimal usage.
- Check your permalink settings (General -> Permalinks) and set
Postname save changes to re-create your .htaccess file.
- If you're using a service like CloudFlare, make sure to disable auto minification. For more information, please check this guide (https://xthemetips.com/using-cloudflare-rocket-loader-with-x-pro-and-x5/928/).
Also you can try increasing your PHP Memory limit. You can do this by editing your wp-config.php file which can be located under the root of your WordPress installation.
Add the following lines into that file.
define( 'WP_MEMORY_LIMIT', '512M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
You can add it before the line
/*That's all, stop editing! Happy Blogging. */
Also follow our troubleshooting guide here (https://theme.co/apex/forum/t/troubleshooting-builder-preview-warnings/14404).
If it does not helps, please share website credentials in a secure note for us to take a closer look.