"A contact group with this name already exists" error when you delete a contact and then sign back in Skype for Business

Symptoms

Assume that you delete a contact from the Groups tab of the contact list in Microsoft Skype for Business. When you sign out and then sign back in the client, the deleted contact is added back to the contact list as a contact group with the same name, and you receive the following error message:

Additionally, the contact can't be deleted in the Relationships tab.

Resolution

To fix this issue, install the June 7, 2016 update (KB3115033) for Microsoft Lync 2013 (Skype for Business).