El log que me aparece en la llamada es:
-- Remote UNIX connection disconnected
== Using SIP RTP TOS bits 184
== Using SIP RTP CoS mark 5
> 0x7f66c870a110 -- Strict RTP learning after remote address set to: 94.23.83.46:26218
-- Executing [960624328@from-trunk-sip-00DEGESTEC:1] Set("SIP/00DEGESTEC-0000008c", "GROUP()=OUT_3") in new stack
-- Executing [960624328@from-trunk-sip-00DEGESTEC:2] Goto("SIP/00DEGESTEC-0000008c", "from-trunk,960624328,1") in new stack
-- Goto (from-trunk,960624328,1)
-- Executing [960624328@from-trunk:1] Set("SIP/00DEGESTEC-0000008c", "FROM_DID=960624328") in new stack
-- Executing [960624328@from-trunk:2] Goto("SIP/00DEGESTEC-0000008c", "s,1") in new stack
-- Goto (from-trunk,s,1)
-- Executing [s@from-trunk:1] ExecIf("SIP/00DEGESTEC-0000008c", "0?Set(FROM_DID=s)") in new stack
-- Executing [s@from-trunk:2] Gosub("SIP/00DEGESTEC-0000008c", "sub-record-check,s,1(force,s,always)") in new stack
-- Executing [s@sub-record-check:1] Set("SIP/00DEGESTEC-0000008c", "REC_POLICY_MODE_SAVE=") in new stack
-- Executing [s@sub-record-check:2] GotoIf("SIP/00DEGESTEC-0000008c", "1?check") in new stack
-- Goto (sub-record-check,s,7)
-- Executing [s@sub-record-check:7] Set("SIP/00DEGESTEC-0000008c", "MON_FMT=wav") in new stack
-- Executing [s@sub-record-check:8] GotoIf("SIP/00DEGESTEC-0000008c", "1?next") in new stack
-- Goto (sub-record-check,s,11)
-- Executing [s@sub-record-check:11] ExecIf("SIP/00DEGESTEC-0000008c", "0?Return()") in new stack
-- Executing [s@sub-record-check:12] ExecIf("SIP/00DEGESTEC-0000008c", "1?Set(REC_POLICY_MODE=always)") in new stack
-- Executing [s@sub-record-check:13] GotoIf("SIP/00DEGESTEC-0000008c", "0?force,1") in new stack
-- Executing [s@sub-record-check:14] Set("SIP/00DEGESTEC-0000008c", "REC_STATUS=INITIALIZED") in new stack
-- Executing [s@sub-record-check:15] Set("SIP/00DEGESTEC-0000008c", "NOW=1531124432") in new stack
-- Executing [s@sub-record-check:16] Set("SIP/00DEGESTEC-0000008c", "DAY=09") in new stack
-- Executing [s@sub-record-check:17] Set("SIP/00DEGESTEC-0000008c", "MONTH=07") in new stack
-- Executing [s@sub-record-check:18] Set("SIP/00DEGESTEC-0000008c", "YEAR=2018") in new stack
-- Executing [s@sub-record-check:19] Set("SIP/00DEGESTEC-0000008c", "TIMESTR=20180709-102032") in new stack
-- Executing [s@sub-record-check:20] Set("SIP/00DEGESTEC-0000008c", "FROMEXTEN=unknown") in new stack
-- Executing [s@sub-record-check:21] Set("SIP/00DEGESTEC-0000008c", "CALLFILENAME=force-s-unknown-20180709-102032-1531124432.1816") in new stack
-- Executing [s@sub-record-check:22] Goto("SIP/00DEGESTEC-0000008c", "force,1") in new stack
-- Goto (sub-record-check,force,1)
-- Executing [force@sub-record-check:1] GosubIf("SIP/00DEGESTEC-0000008c", "1?record,1(force,always,unknown)") in new stack
-- Executing [record@sub-record-check:1] Set("SIP/00DEGESTEC-0000008c", "AUDIOHOOK_INHERIT(MixMonitor)=yes") in new stack
-- Executing [record@sub-record-check:2] MixMonitor("SIP/00DEGESTEC-0000008c", "2018/07/09/force-s-unknown-20180709-102032-1531124432.1816.wav,,") in new stack
-- Executing [record@sub-record-check:3] Set("SIP/00DEGESTEC-0000008c", "REC_STATUS=RECORDING") in new stack
== Begin MixMonitor Recording SIP/00DEGESTEC-0000008c
-- Executing [record@sub-record-check:4] Set("SIP/00DEGESTEC-0000008c", "CDR(recordingfile)=force-s-unknown-20180709-102032-1531124432.1816.wav") in new stack
-- Executing [record@sub-record-check:5] Return("SIP/00DEGESTEC-0000008c", "") in new stack
-- Executing [force@sub-record-check:2] Return("SIP/00DEGESTEC-0000008c", "") in new stack
-- Executing [s@from-trunk:3] Set("SIP/00DEGESTEC-0000008c", "CHANNEL(language)=es") in new stack
-- Executing [s@from-trunk:4] Gosub("SIP/00DEGESTEC-0000008c", "app-blacklist-check,s,1()") in new stack
-- Executing [s@app-blacklist-check:1] GotoIf("SIP/00DEGESTEC-0000008c", "0?blacklisted") in new stack
-- Executing [s@app-blacklist-check:2] Set("SIP/00DEGESTEC-0000008c", "CALLED_BLACKLIST=1") in new stack
-- Executing [s@app-blacklist-check:3] Return("SIP/00DEGESTEC-0000008c", "") in new stack
-- Executing [s@from-trunk:5] Set("SIP/00DEGESTEC-0000008c", "CDR(did)=960624328") in new stack
-- Executing [s@from-trunk:6] ExecIf("SIP/00DEGESTEC-0000008c", "1 ?Set(CALLERID(name)=655463605)") in new stack
-- Executing [s@from-trunk:7] Set("SIP/00DEGESTEC-0000008c", "CHANNEL(musicclass)=default") in new stack
-- Executing [s@from-trunk:8] Set("SIP/00DEGESTEC-0000008c", "MOHCLASS=default") in new stack
-- Executing [s@from-trunk:9] Set("SIP/00DEGESTEC-0000008c", "CALLINGPRES_SV=allowed_not_screened") in new stack
-- Executing [s@from-trunk:10] Set("SIP/00DEGESTEC-0000008c", "CALLERPRES()=allowed_not_screened") in new stack
-- Executing [s@from-trunk:11] Goto("SIP/00DEGESTEC-0000008c", "app-announcement-1,s,1") in new stack
-- Goto (app-announcement-1,s,1)
-- Executing [s@app-announcement-1:1] GotoIf("SIP/00DEGESTEC-0000008c", "0?begin") in new stack
-- Executing [s@app-announcement-1:2] Answer("SIP/00DEGESTEC-0000008c", "") in new stack
> 0x7f66c870a110 -- Strict RTP switching to RTP target address 94.23.83.46:26218 as source
-- Executing [s@app-announcement-1:3] Wait("SIP/00DEGESTEC-0000008c", "1") in new stack
-- Executing [s@app-announcement-1:4] NoOp("SIP/00DEGESTEC-0000008c", "Playing announcement Aviso de la grabacion") in new stack
-- Executing [s@app-announcement-1:5] Playback("SIP/00DEGESTEC-0000008c", "custom/AvisoGrabacion,noanswer") in new stack
[2018-07-09 10:20:34] WARNING[31848][C-00000061]: mp3/interface.c:217 decodeMP3: Junk at the beginning of frame 49443303
-- <SIP/00DEGESTEC-0000008c> Playing 'custom/AvisoGrabacion.slin' (language 'es')
> 0x7f66c870a110 -- Strict RTP learning complete - Locking on source address 94.23.83.46:26218
== MixMonitor close filestream (mixed)
== End MixMonitor Recording SIP/00DEGESTEC-0000008c
He probado a poner lo que comentaba venturinog, pero me hace lo mismo.