EPM does not allow more than one hotdesk entry

If you try to enter more than one hotdesk station in extension mapping it sends a error that the MAC address of "" is a duplicate. This applies also if you try to rebuild the files for more than one hotdesk station if more than one is currently logged out and if you try to import a CSV file that does not include the MAC addresses. (the first one will load but then errors out for the rest saying a MAC address of "" is a duplicate). Obviously more than one logged out hotdesk station is allowed as I can log multiple ones out, and they show on the list as no mac address, but if I update or add stations to the list with no MAC address and there are one or more already there, it will throw the error and not refresh the list, but if I refresh the browser page it was added to the list anyway.