Do all three numbers have a unique port #?
My number and cloned line have 5060 and 5061.
Just wondering what the soft phone has and if it overlaps the ATA port?


MEANDERING THOUGHT:
I theory a good router would successfully get many ATAs all set to 5060 to the right place as long as they had unique IP addresses. Some routers it seems can get confused routing NAT IPs. Port forwarding is sometimes used to overcome NAT and firewall issues. Of course you need unique ports to unique addresses to do port forwarding. I personally hate a need for port forwarding - I would replace a router before living long-term with port forwarding.