[arm-allstar] Node won't connect - Registration problem

[Randy Neals]

I have a node that will work for several days just fine, and then it takes
a spell where it won't connect.
It's in one of those spells right now - the iax2 registry shows
registration timeout.

We rebooted the Raspberry Pi about 12 hours ago. No change.
I stopped and started Asterisk about 20 minutes ago. No change.

===== iax2 show registry =====
ActionID: cpAction_849519009
Host                  dnsmgr  Username    Perceived
Refresh  State67.215.233.178:4569   Y       28706
60  Timeout67.215.233.178:4569   Y       28705                    60
Timeout
--END COMMAND--

At the same site, on the same LAN, I have a second Raspberry Pi
running the exact same HamVoip release and controlling a 3rd repeater.
It's registering fine.

===== iax2 show registry =====
ActionID: cpAction_87809639
Host                  dnsmgr  Username    Perceived
Refresh  State67.215.233.178:4569   Y       28702
72.142.154.238:4570        60  Registered
--END COMMAND--

The Internet connection is via NAT router to a a single public IP which is
dynamic. I have port 4569 mapped to the LAN IP of the first server, and
port 4570 mapped to the LAN IP of the second server. I looked at the router
NAT configuration to ensure that was working correctly. Here's a screen
shot of the NAT config. https://pasteboard.co/GLvlGZr.png Here's a partial
screen shot of the connection status. https://pasteboard.co/GLvkq09.png If
you have any pointers on what I should look at next, that would be
appreciated. Randy, W3RWN