Please try to check it by deactivating all third-party plugins (except Toolset related) and switching back to the Default Theme (e.g. Twenty Sixteen theme) to see for any possible conflicts with any of the plugins or themes?
If still issue persists, please provide temporary access WP-Admin Login and FTP login info to your site. Your next answer will be private which means only you and I have access to it.
=== Please backup your database and website ===
✙ I would additionally need your permission to de-activate and re-activate Plugins and the Theme, and to change configurations on the site. This is also a reason the backup is really important.
✙ Please add the Link to the page where I can see the issue.
I have checked your site and found that MemberPress plugin conflicts with Toolset. When I deactivated MemberPress Basic plugin then there is no duplicated category terms: hidden link
I would suggest to please contact that MemberPress Basic plugin author and ask them to check. Thank you for your understanding.