It looks like your site is under CloudFlare, please log in to CloudFlare dashboard and do the following:
First exclude the Cornerstone builder from being cache by using this pattern
*yourdomain.com/x/* follow this article on how you can add a page rule (exclude) on your CloudFlare account.
Next disable the CloudFlare's JS and CSS minification option, read this article., X theme JS and CSS files are already minified so you don't need this feature (this is actually the feature that is causing the issue, breaking the CSS files.)
Lastly purge everything from the cache, also clear your browser's cache to make sure that there is no cache involve when you load your pages.
Another thing, please update the X extensions (X – Content Dock, X – Custom 404, and X – Under Construction).
To update the Extensions to the version that is supported by the theme:
- Ensure your theme is validated so Extensions can be installed automatically
- Deactivate and delete the extensions, from the plugins panel.
- On the X > Validation > Extensions locate and install the extensions that you need.
- Visit "Plugins" panel in your Dashboard to activate the newly installed version.
Because all of the plugin settings are stored in the database, and because version 2.x will migrate settings from older versions, its safe to use this method of deleting the previous version. But always keep a backup of your entire site just to be safe.
Let us know how it goes,