we have an issue with t38_gateway where calls which should be transcoded from PCMA to t38 get hangup non-deterministic. It doesn’t matter if there is only one call or if there are hundrets of calls on the freeswitch. Sometimes it happens that we get several faxes transcoded but then we again have several faxes which don’t go through. problem exists (tested) on FreeSWITCH 1.6 and FreeSWITCH 1.10. this is the dialplan section where t38_gateway is set up for b-leg on an inbound call: <context name="hosted_numbers"> <extension name="43732601458-DDI" continue="true"> <condition field="${outside_call}" expression="^true$" break="never"/> <condition field="${dialed_extension}" expression="^(43732601458)(\d{0,4})$“> ... <action application="set" data="refuse_t38=true"></action> <action application="export" data="fax_enable_t38=true"></action> <action application="export" data="nolocal:sip_execute_on_image=t38_gateway self nocng"></action> <action application="bridge" data="{sip_cid_type=pid,sip_contact_user=accountcode,absolute_codec_string='PCMA@20i,PCMU@20i,G729'}sofia/internal/accountcode@10.23.101.10^+${dialed_extension}@10.23.101.10"></action> ... </condition> </extension> </context> tested freeswitch versions: FreeSWITCH Version 1.6.20-37-987c9b9~64bit (-37-987c9b9 64bit) FreeSWITCH Version 1.10.1-release-12-f9990221e6~64bit (-release-12-f9990221e6 64bit) -> version where logfile is created this is the debug section where the call gets hung up: 287b2821-05a1-4ff6-9449-dac913b803eb 2019-12-03 20:32:23.257123 [DEBUG] switch_core_media.c:5285 sofia/internal/46wp809758@10.23.101.10 T38 IS POSSIBLE on request cc222460-f51e-453e-9a09-c2e97e6b8af9 2019-12-03 20:32:23.259118 [ALERT] switch_rtp.c:1595 sofia/external/+4318033811@193.32.51.146:5060 audio stat 100.00 673/673 flaws: 0 mos: 4.50 v: 0.00 0.00/0.00 cc222460-f51e-453e-9a09-c2e97e6b8af9 2019-12-03 20:32:23.259118 [DEBUG] switch_ivr_bridge.c:824 sofia/internal/46wp809758@10.23.101.10 ending bridge by request from write function cc222460-f51e-453e-9a09-c2e97e6b8af9 2019-12-03 20:32:23.259118 [DEBUG] switch_ivr_bridge.c:916 BRIDGE THREAD DONE [sofia/external/+4318033811@193.32.51.146:5060] 287b2821-05a1-4ff6-9449-dac913b803eb 2019-12-03 20:32:23.260120 [ALERT] switch_ivr_bridge.c:1893 sofia/internal/46wp809758@10.23.101.10 receive message [UNBRIDGE] full logfile of call is enclosed fsctl debug settings: fsctl loglevel debug fsctl debug_level 9