ATA to softphone fax; Asterisk not mediating T38 correctly?

I’m trying to isolate my T38 issues, so I am faxing from an ATA (obiHai-200) to the Kapanga softphone, and taking packet captures on the pbx and the machine running the softphone.
Looking at the call flows, it seems like the T38 messages sent to asterisk from either side are not being forwarded to the other device.
Any suggestions on what things I should look at to troubleshoot this problem. I have taken a log of everything, with ‘sip set debug on’ as well as debug and verbose levels at 5. I don’t really know what to look for in the log–the only thing I see suspicious is that the v=0 SDP description is coming up “UNSUPPORTED OR FAILED”.
This is running with FreePBX on Asterisk 11.5.
I do have a “t38pt_udptl=yes,redundancy,maxdatagram=400” line in my sip_general_additional.conf and I also added it in the sip_general_custom.conf… just in case. I also have the various udptl settings in the udptl_custom.conf.

Capture on pbx

Capture on softphone host