So far turning of the port triggering and leaving the Upnp active has worked. Still get moterate connection on my wireless connected 2nd Xbox though. I hard reset when i last finished using it so we'll see if it opens up next time it use.
Thanks for the pointing out the conflict between Upnp and port forwarding.
In WAN Setup on the router settings page, you can select NAT Filtering to Open and it may help you get Open NAT on both Xbox consoles.