Something very strange must have happened. Comcast would normally ring for at least a minute (60000 ms) before giving up. Possibilities include: You have a setting at Comcast to send the call to voicemail after only 5 seconds (you might have done this if your PBX normally answers immediately with an IVR and you’re using Comcast voicemail as failover if the PBX is down or inaccessible). Something or someone else bridged on the line picked up (fax machine, alarm system, your wife, etc.). A (possibly related) technical problem caused the OBi to trip the ring but not forward the call to the PBX.
What does Call History show for the 5000 ms case?
I don’t use a special syslog server, preferring to just use Wireshark. That way, SIP packets copied to syslog (turn on X_SipDebugOption for the SPx in question) get correctly parsed.