Assign case role (Manage Case screen) doesn't work on some case role rows

Using the sample case configuration, if I create a case (type = Adult Day Care Referral), I can assign a contact to the 2nd Case Role in the list (Health Svcs Coord). BUT, if I try to assign a contact to the THIRD case role (e.g. Benefits Specialist) - the auto-complete widget doesn't work properly (I get doubled-up listings) and although I can select a contact from the lower listing - I get 'unassigned' afterwards (no relationships is created).

Screen shot attached to clarify.