Firewall/NAT

M0n0wall newbie here.
Breakin' my head trying to enable remote VoIP endpoints for our InterTel Axxess switch.
“Someone” began this effort before I got here, and successfully opened ONE of the ports this setup requires.
I'm just trying to open ONE more port with identical Rule/NAT combo; no luck.
See below for info on the two Rule/NAT combos I'm working with.
Can't figure out for anything WHY one rule works, the other doesn't.
The logs are no help. 
I have no 'BLOCK'/'REJECT' rules set up and rearranging the order seems to have no effect.
Thanks in advance for any tips you can provide.

This Rule/NAT combo works; port is open.
Firewall:Rules:WAN
Proto: TCP
Source: *
Source Range: *
Dest: 192.168.1.132
Port: 5566

Firewall:NAT:Inbound
Ext Address: Interface Address
IF: WAN
Proto:TCP
Ext. Port Range:5566
NAT IP:192.168.1.132
Int. Port Range:5566

THIS Rule/NAT combo does NOT work; port is NOT open.
Firewall:Rules:WAN
Proto: TCP
Source: *
Source Range: *
Dest: 192.168.1.132
Port: 5567

Firewall:NAT:Inbound
Ext Address: Interface Address
IF: WAN
Proto:TCP
Ext. Port Range:5567
NAT IP:192.168.1.132
Int. Port Range:5567

An update:  I have created a 1:1 NAT for the InterTel Axxess switch, and am now seeing the InterTel 8622 endpoint attached remotely to the switch.
I can place and receive calls with this endpoint. Yay!
Trouble is, I get no audio, Boo!

Public IP 71.40.x.x is 1:1 NAT'd to 192.168.1.132. Ok fine.
Now, automagically, calls pass through AND port 5566 (for which I no longer have a rule configured) shows open when I do a zenmap scan from off the LAN.
Do I still need to create NATs and Rules for the ports I need open?
I have rebooted m0n0wall, reset state...Next step?...Float test this sucker and replace it with something 'predictable'.

So...now I've updated my firmware from v1.235b to v1.31.
Didn't think it would have any effect, but I'm running out of ideas.

Does m0n0wall prefer goats or chickens re: ritual sacrifice? 

Wow...this is turning into a diary...
Question I have now is:
I have my 1:1 NAT set up from my InterTel Axxess 5000 switch and my n0n0wall,
There are ports I need to open (5070 TCP, 5004-5569 UDP). Do I/Can I open these for the 1:1 NAT?
I get the feeling I cannot open these ports for the 1:1 NAT; but I don't know.

Other question I have:
I can open/close port 5566 TCP all day long to the WAN interface.
I cannot open other ports; need 5004-5569 UDP, and 5070 TCP.
What gives here?  This is practically a new installation at this point, but still it behaves the same.
Anybody?