Hello There,
Thanks for writing in! I would recommend that you create a staging site. This is very useful because you can test drive any X updates in the staging area, do the customizations and troubleshooting without disrupting your live site. Once everything is perfect, you can easily and flawlessly proceed the update in the live site. To know how to create a staging area, please check out these articles:
http://www.wpbeginner.com/wp-tutorials/how-to-create-staging-environment-for-a-wordpress-site/, https://maintainn.com/2015/02/how-to-create-a-staging-site-for-wordpress/
By the way, I have check your urls and I can see that you have updated Cornerstone to version 2.1.3. Please keep in mind that X 4.6.4 will only with with Cornerstone 1.3.3. You will have to update X theme too. We have just released X 5.2.3 and Cornerstone 2.1.4. It is now available in automatic updates. You can now update to this latest version. This latest release contains fixes for several issues so be sure to check out the changelog (http://theme.co/changelog/).
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.
And regarding X theme refunds;
All sales are handled through ThemeForest, and their parent company Envato handles all refund requests. You can read more about their process here.
Hope this helps.