T38 Fax Mode using PJSIP trunk fails - Calls dropped prematurely from conflicting Reinvite

I’m using T38fax.com configured as a PJSIP trunk as follows:

[root@vpbx01 vitalpbx]# asterisk -x"pjsip show endpoint T.38PJSIP" | grep t38
Contact: T.38PJSIP/sip:sip.t38fax.com:5080 302605580b Avail 50.038
t38_bind_udptl_to_media_address : false
t38_udptl : true
t38_udptl_ec : redundancy
t38_udptl_ipv6 : false
t38_udptl_maxdatagram : 400
t38_udptl_nat : true

This carrier is setup to initiate the T.38 reinvite. This is causing faxes to fail as it seems vitalpbx sends a conflicting reinvite at the same time and the call is then terminated with at 488 Not acceptable here. This happens on about 50 percent of the outbound fax calls. The calls logs show "FAX Sending: failed. Error desc: The call dropped prematurely. This may happed when the call first connects or halfway through faxing.

Is there any way to turn off sending the T.38 reinvite from Vitalpbx and allow the carrier to initiate this only? Any other ideas on what could be causing this?

Also, can anyone provide a recommended carrier that is proven to work with vitalpbx and T.38 reliably that I can configure?

For reference:
values in res-fax.conf are:
[general]
minrate=4800
maxrate=9600
modems=v27,v29

and udptl_general.conf are:
[general]
udptlstart=10000
udptlend=10999
T38FaxUdpEC=t38UDPRedundancy