Can you describe in more detail your network setup?
It looks like you have a SIP trunk pointing to the VoiceGuide IVR, and looks like you are registering it at restart time (but not Authenticating?).
It looks like the IP address of VoiceGuide system is 192.168.1.143, and IP address of the Avaya IPOffice which is providing the SIP trunk is 192.168.5.1
What is the 192.168.5.204 address of?
Is 192.168.5.204 maybe the address to which the calls are routed it initially?, and then 192.168.5.204 routes call to 192.168.5.1 which then routes call to 192.168.1.143 ?
It looks like the system at 192.168.5.204 and the system that is sending call to 192.168.5.204 is not passing on the number dialed, but is placing the 192.168.5.204 in the DNIS field.
Looking at WireShark trace will let you better see what information is supplied with the call, and sounds like you may want to run WireShark traces on traffic between 192.168.5.204 and the Avaya IPOffice, and probably on traffic arriving into the 192.168.5.204 as well.