Thank you for writing in, no, we have not received a ticket with this same issue. Currently, your site is up, Although your X and Cornerstone is not updated to the latest version (X 7.1.2 / CS 4.1.2) I don't see that being the cause of the issue, your Wordpress version (5.3) is up to date as well, so I don't really see the issue on your site at the moment.
Would you mind providing more information on why the provider said it's a theme issue? Can you share an error log?
To update X and Cornerstone, please follow the following link.
Updating Your Themes and Plugins
Remember to clear all your caching features (plugin, server-side, CDN, and browser's cache) after updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.