Thank you for writing in, your Cornerstone is updated (2.1.7), but your XTheme is outdated (4.5.2). Please update X to the latest version (5.2.5) to make sure that this is not an incompatibility issue.
Updating Your Themes and Plugins
Remember to clear all caches (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.
Let us know how it goes,