I don't know exactly how to approach this, it's never happened to me. Off the top of my head, what if you configure the MCU to not use the VCS, and configure TMS to have the MCU dial out to the endpoints directly via IP address. Within TMS, you'd edit the settings of the MCU, and at the bottom under "TMS Scheduling Settings" deselect everything but "Allow Outgoing IP Address Dialing".
Suggest you move this thread to the TelePresence section of the forums where these devices are actively discussed. You can move the thread by editing it and changing the categories at the bottom of the page.