Hello, Zoho One user here.
I have the following persistent problem: when an end-user (Help Center User) is added to a group, it can never be removed from it. When editing the user and hovering over the group name, it shows the red X, and when you click it the group does disappear. However when you click save, the group immediately reappears, and you get the following popup: 

Uh-oh, something went wrong while removing the Advanced Registered Users group.

This happens to the master admin, so it is not a matter of permissions.

Please advise.