Inbound Routes CID name prefix is inconsistant

I am using the CID name prefix feature in Inbound Routes to prepend the caller ID name on inbound calls. Each of my routes has a different CID name prefix. All of the destinations for the routes are one of several different but similar queues. The queues differ in the agents assigned to the queues but are otherwise the same. All of the agents are SIP extensions, 95% of them are on the LAN.

The T-1 card is a Digium 1TE420BF (4 port PCI Express with echo cancellation). FreePBX, Asterisk, and dahdi-linux-complete-2.6.0.

I have a SIP trunk for testing but my main lines are T-1 PRIs. The calls on the SIP trunks seem to reliably prepend CID but the T-1 calls do not (though we do a lot more calls on T-1 compared to test calls on SIP). The CID prefix is inconsistent. The CID name is always delivered to the user’s phone but sometimes it has the CID name prefix and sometimes it does not. This happens on all of the routes.

An additional wrinkle is that it seems like certain callers have very good CID prefix hits while others very poor. For example, one IT person places inbound test calls from his Verizon cell phone while another IT person places inbound calls from his AT&T cell phone. When the agent receives the call from the Verizon cell phone more than half the time the CID name is just as delivered while with the AT&T cell phone the CID name is prefixed correctly most of the time. This is observed from various land line callers too but is easy to test with our cell phones.

Any thoughts on where to look or what to change?

Any thoughts?

try including a trace of a call where the prefix is included and another trace where it is not. If possible, on the same inbound number being dialed but either way, something so that we can see if it’s an issue in the dialplan or some other reason shy it’s not getting prepended.