Source Monitor vs Program Monitor Mercury Transmit

I'm expereincing a new issue where both my program panel and source panel are being displayed via mercury transmit on my reference monitor. 

Previously only the program panel was displayed on my second monitor via mercury transmit which meant that only the main edit would be displayed while I was free to view clips in source panel, make in and out points and drag clips ontot the timeline without that source panel slecetion replacing the main timeline preview on my second screen.

Any idea how to stop the source panel also being trasmitted to the reference monitor?