Outgoing (fax) calls have begun being redirected to a fax extension

I maintain a server without a lot of telephony experience. Recently (e.g. in the last 8 weeks) we’ve had several outgoing fax calls dropping rather than connecting successfully.

They’re fax numbers that we’ve previously successfully connected to. I’ve made test calls from a desk phone, and from fax machines.

Asterisk 1.6.0.10
Linux 2.6.18-128.1.10.el5
We also run avantfax/hylafax on this server. I’m not sure if this is relevant

I have VOIP service and a PRI. These particular calls are going out on the PRI.

Here’s a snip from a successful call:

– Called g11/1866XXXXXXX
– DAHDI/1-1 is proceeding passing it to SIP/242-b615a520
– DAHDI/1-1 is making progress passing it to SIP/242-b615a520
– DAHDI/1-1 is ringing
– DAHDI/1-1 answered SIP/242-b615a520
== Using SIP RTP TOS bits 184
== Using SIP RTP CoS mark 5
== Using SIP VRTP TOS bits 136
== Using SIP VRTP CoS mark 6

Here’s what I found in a failed call:

– Called g11/1972XXXXXXX
– DAHDI/2-1 is proceeding passing it to SIP/242-b615a520
– DAHDI/2-1 is making progress passing it to SIP/242-b615a520
– DAHDI/2-1 is ringing
– DAHDI/2-1 answered SIP/242-b615a520
– Redirecting DAHDI/2-1 to fax extension

I’ve done some research, which led me to /etc/asterisk/chan_dahdi.conf and I see:

faxdetect:both

…which I could modify to only detect incoming, however these are calls that were never previously affected, and as nothing has changed, I don’t think I should be making any changes.

Thanks in advance if anyone can provide some assistance. I’ll be glad to provide additional information as requested.