From the directory it is possible to add a member to two or more of the small groups. and they show up in the small groups lists accordingly.
If then from the Groups menu you add the member to a particular Group or Just save the entry then all other groups are removed from that members entry.
I can accept that unattached cannot be added when any other group is enabled but i have several members who are in more than one group.
It is possible to edit each members directory entry to re-add them but it is a painful task.