Looks like a fault with the duplicate group detection.

When I make a change to a group, such as adding or removing its description, a number is appended to the group name that is incremented on each subsequent saving of the group.

E.g. a group called Example. If I edit it, adding a description, when I press save it is listed as Example1. If I edit it again and remove the description, when I save it is listed as Example2.