Reassigning case roles doesn't work?

[norris]

On my Joomla system, and on demo sandbox:

When I create a case, and open the Roles area: If a role is already assigned to someone and I click the edit button, it acts as if I should be able to reassign the role to another contact.  I search for a new contact to whom to assign the role, then hit Save.  But nothing changes.

I can work around this by first deleting the assigned contact, then adding the new one.