Hi, I have sended another email to the list with attachments. I think that the list not accepts attachments, sorry. I have several FreeSWITCH's (latest version from deb packages: 1.10.1 -release-12-f9990221e6) and I have problems with faxes in proxy media (in bypass-media works). In the sofia.conf.xml I have setted the param t38-passthru=true If the flow is: 1. Initial INVITE 2. Re-Invite from one of the legs with t38 sdp Result: works But if the flow is: 1. Initial INVITE 2. Re-invite from one of the legs changing the media (at answer) 3. Re-invite from one of the other legs with t38 sdp Result: not works I tried with "soa_enable=false" without luck. FreeSWITCH seems that hangs the sip transaction. This capture is the first reinvite (in the flow, the "showing" line): https://pastebin.com/raw/X4zrUr4k This capture is the reinvite with the t38 negotiation sended by the receiver (Grandstream ATA): https://pastebin.com/raw/KCXD51aH And this with the response (200ok) accepting the t38 negotiation): https://pastebin.com/raw/ifqtPN8L How I can debug the problem? Best regards