Hello, Tom
Please try to disable all the third-party plugins (including cache plugins), that do not come bundled with XStore https://xstore.helpscoutdocs.com/article/36-included-plugins , clear the cache of the browser, and check then. Maybe one of the additional plugins is the reason for the problem.
It looks like a cache problem, so try to temporarily disable cache from the server side and CDN also.
We look forward to hearing from you.
Kind Regards,
8Themes Team