Problem with PJSIP and T38


I need help to solve a problem that I am having using Asterisk 13, PJSIP and T38.

My setup is as follows:
SIP Provider --> Asterisk 13 --> Patton --> Physical Fax
I need to get the fax directly in T38 to Patton.

The provider sends me the fax in T38.
If I receive the T38 fax on Asterisk (using a hylafax device), I can properly receive the fax.
If I send a T38 fax with Asterisk (using a hylafax device) directly to the Patton, I receive it correctly on the physical fax.

Instead, if I route, through Asterisk, the t38 fax call received by the provider to the Patton, I can not receive anything.
From UDPTL debug I can see the flow of some udptl packages from the provider to Asterisk, but I see no udptl package from Asterisk to the Patton.
From PJSIP logs, it seems that the T38 is properly negotiated by both parties.

How to ensure that the fax, received by asterisk from the provider with T38 protocol, is routed to the Patton using again T38 protocol?