Well, you can’t really use port remapping.
When using SIP, each device or side formulates their respective messaging by understanding where they reside in a network and then comparing the received messaging to understand how to respond to the requesting device.
When sending a message, there are two critical headers and these are the “Contact” and the “Connection” headers. The contact header tells the other end to what IP and port it should use when responding for SIP messages and the connection header does the same thing, but for the RTP stream. With a PBX the connect and connection header will usually be the same, but when messaging to a provider, the contact and connect headers may not be the same IP usually due teh volume of calls and the need to be able to let a different server handle the media (RTP).
So, in the UCM you tell it what its public IP is and then you define the local network LAN. When the UCM sees a message from the LAN it will respond and tell the LAN device to use the UCM’S private IP and if the UCM sees a message from something other than the LAN then it will use the gateway to tell the non-local device to use the UCM’s public IP.
As far as I am aware, if you want to use something other than the default 5060, then you should set both to the desired port. It is my understanding, and I could be wrong as the manual does not discuss both settings, is that the NAT port setting is used formulate the port to be used in the external messaging. The general setting is used to tell the UCM what port to bind the SIP stack to. I am of the impression that the UCM is not capable of binding the SIP stack for a given transport to more than one port. So, it sounds like you were telling the external world to use port 5070 and when the responses came back on 5070, the UCM was bound to 5060. When you tried to re-map 5070 to 5060, the messaging was still set to 5070 and I am guessing that even if it saw the message physically arriving on 5060, the contact header was incorrect and perhaps this caused the issue. I am uncertain about this not seeing it first hand or seeing a pcap, but hey, it’s a guess.
You can’t really remap as the device will expect to see the response on the port in the connect header when it sent the initial query.