FAXing with T.38 Trunk (Asterisk

I have an ATA attached to a fax machine that I’m not able to reliably send or receive T.38 faxes with. The trunks (Broadvox) are configured for T.38 and so is the ATA (Linksys SPA3102).

Here is the environment:
AsteriskNOW 1.7.1

Here is the layout of the network:
Broadvox --> WAN --> Firewall (NAT) --> ATA --> FAX Machine

I have verified by taking captures that the transmission switches over to T.38 but most attempts result in a hangup around 30 seconds into the call.

There are a variety of issues found in the Asterisk logs (included below) but in the research I’ve done I haven’t found any resolution.

Can anyone help point me in the right direction?

WARNING[5836] udptl.c: (SIP/4232879579): UDPTL asked to send 41 bytes of IFP when far end only prepared to accept 38 bytes; data loss will occur.You may need to override the T38FaxMaxDatagram value for this endpoint in the channel driver configuration.

WARNING[22599] rtp.c: RTP Read too short [Mar 24 14:44:58] WARNING[22599] rtp.c: RTP Read too short

WARNING[24064] udptl.c: T38FaxUdpEC in udptl.conf is no longer supported; use the t38pt_udptl configuration option in sip.conf instead.

WARNING[24064] udptl.c: T38FaxMaxDatagram in udptl.conf is no longer supported; value is now supplied by T.38 applications.

Here is udptl.conf:

 ; UDPTL Configuration (UDPTL is one of the transports for T.38)
 ; UDPTL start and UDPTL end configure start and end addresses
 ; Whether to enable or disable UDP checksums on UDPTL traffic
 ; The error correction type to be sent
 ;T38FaxUdpEC = t38UDPFEC
 T38FaxUdpEC = t38UDPRedundancy
 ; The maximum length of a UDPTL packet
 T38FaxMaxDatagram = 200
 ; The number of error correction entries in a UDPTL packet
 udptlfecentries = 1
 ; The span over which parity is calculated for FEC in a UDPTL packet
 udptlfecspan = 3

Here is sip_general_custom.conf: