The MAC isn't the only thing that has to be the same in both the DOL and another stb app. The server keeps track of other information that is created when an app initially connects to the server (or it used to.)
If you want to connect to the server one-at-a-time, you should use the playlist settings (i.e. no MAC) and use the new official andriod app on your boxes, otherwise you will need to do an IPTV reset every time you view the service on a different box.