Hello,
We recommend that you disable all third-party plugins that are not included with XStore (https://www.8theme.com/documentation/xstore/plugins/included-plugins/). After doing so, please clear your browser’s cache and check again. It is possible that one of these additional plugins is causing the issue.
Additionally, may we ask which browser you are using? We have tested the scrolling functionality on your website using Google Chrome and did not notice any issues.
Warm Regards,
The 8Theme Team