If one edits a NIC that is assigned on a Virtual Machine, changes the name of the NIC and clicks Save, the end result is the VM has a brand new NIC assigned to it with the new name and the old NIC is also assigned to it.  This would not be much of a problem, however they both have the same MAC address.

The expectation is that it should delete the old NIC and create a new one if you change the name of the NIC.  If this is not an option and a new NIC must be created, attempting to save the NIC should fail stating that an existing NIC already has the requested MAC address