GOautodial Open Source Omni-channel Contact Center Suite

Hi guys,
I've got an issue on an outbound campaign. The Agent is connect with webrtc on the agent interface. The call is connected with a prospect. There's no codec or NAT issue.The session start and sometimes the call is dropped. I checked sip traces from my carrier the call is disconneted on our side. I cheked asterisk logs I found that :

Sep 22 18:03:37] VERBOSE¹⁹⁶⁰⁵ dial.c: Called 5550142514002@default
[Sep 22 18:03:37] VERBOSE¹⁹⁶⁰⁶[C-0000508f] pbx.c: Executing [5550142514002@default:1] AGI in new stack
[Sep 22 18:03:37] VERBOSE¹⁹⁶⁰⁶[C-0000508f] res_agi.c: AGI Script Executing Application: (EXEC) Options: (Set(_CAMPCUST=29607884))
[Sep 22 18:03:37] VERBOSE¹⁹⁶⁰⁶[C-0000508f] res_agi.c: <Local/5550142514002@default-00002903;2>AGI Script agi://127.0.0.1:4577/call_log completed, returning 0
[Sep 22 18:03:37] VERBOSE¹⁹⁶⁰⁶[C-0000508f] pbx.c: Executing [5550142514002@default:2] Dial("Local/5550142514002@default-00002903;2", "SIP/500033142514002@MT001,,tTo") in new stack
[Sep 22 18:03:37] VERBOSE¹⁹⁶⁰⁶[C-0000508f] netsock2.c: Using SIP RTP CoS mark 5
[Sep 22 18:03:37] VERBOSE¹⁹⁶⁰⁶[C-0000508f] app_dial.c: Called SIP/500033142514002@MT001
[Sep 22 18:03:37] VERBOSE¹⁹⁶⁰⁶[C-0000508f] app_dial.c: SIP/MT001-00002391 is ringing
[Sep 22 18:03:37] VERBOSE¹⁹⁶⁰⁵ dial.c: Local/5550142514002@default-00002903;1 is ringing
[Sep 22 18:03:54] VERBOSE¹⁶⁴⁷[C-0000508f] res_rtp_asterisk.c: 0x7fb434000e00 -- Strict RTP learning after remote address set to: YYY.xxx.zzz.186:51564
[Sep 22 18:03:54] VERBOSE¹⁹⁶⁰⁶[C-0000508f] app_dial.c: SIP/MT001-00002391 answered Local/5550142514002@default-00002903;2
[[Sep 22 18:03:54] VERBOSE¹⁹⁷⁶⁴[C-0000508f] bridge_channel.c: Channel SIP/MT001-00002391 joined 'simple_bridge' basic-bridge <a99e6347-b48d-4053-b070-3e19adf89560>
[Sep 22 18:03:54] VERBOSE¹⁹⁶⁰⁶[C-0000508f] bridge_channel.c: Channel Local/5550142514002@default-00002903;2 joined 'simple_bridge' basic-bridge <a99e6347-b48d-4053-b070-3e19adf89560>
[Sep 22 18:03:54] VERBOSE¹⁹⁷⁶⁴[C-0000508f] res_rtp_asterisk.c: 0x7fb434000e00 -- Strict RTP switching to RTP target address YYY.xxx.zzz.186:51564 as source
[Sep 22 18:03:54] VERBOSE¹⁹⁷⁶⁴[C-0000508f] bridge_channel.c: Channel SIP/MT001-00002391 left 'simple_bridge' basic-bridge <a99e6347-b48d-4053-b070-3e19adf89560>
[Sep 22 18:03:54] VERBOSE¹⁹⁶⁰⁶[C-0000508f] bridge_channel.c: Channel Local/5550142514002@default-00002903;2 left 'simple_bridge' basic-bridge <a99e6347-b48d-4053-b070-3e19adf89560>
[Sep 22 18:03:54] VERBOSE¹⁹⁶⁰⁶[C-0000508f] pbx.c: Spawn extension (default, 5550142514002, 2) exited non-zero on 'Local/5550142514002@default-00002903;2'
[Sep 22 18:03:54] VERBOSE¹⁹⁶⁰⁶[C-0000508f] pbx.c: Executing [h@default:1] AGI") in new stack
[Sep 22 18:03:54] VERBOSE¹⁹⁷⁶⁴[C-0000508f] pbx.c: Executing [8368@default:1] AGI in new stack
[Sep 22 18:03:54] VERBOSE¹⁹⁷⁶⁴[C-0000508f] res_agi.c: AGI Script Executing Application: (EXEC) Options: (Set(_CAMPCUST=29607884))
[Sep 22 18:03:54] VERBOSE¹⁹⁷⁶⁴[C-0000508f] res_agi.c: <SIP/MT001-00002391>AGI Script agi://127.0.0.1:4577/call_log completed, returning 0
[Sep 22 18:03:54] VERBOSE¹⁹⁷⁶⁴[C-0000508f] pbx.c: Executing [8368@default:2] AGI in new stack
[Sep 22 18:03:54] VERBOSE¹⁹⁷⁶⁴[C-0000508f] res_agi.c: Launched AGI Script /usr/share/asterisk/agi-bin/agi-VDAD_ALL_outbound.agi
[Sep 22 18:03:55] VERBOSE¹⁹⁷⁶⁴[C-0000508f] res_agi.c: <SIP/MT001-00002391>AGI Script agi-VDAD_ALL_outbound.agi completed, returning 0
[Sep 22 18:03:55] VERBOSE¹⁹⁷⁶⁴[C-0000508f] pbx.c: Executing [127*000*000*001*8600056@default:1] Goto("SIP/MT001-00002391", "default,8600056,1") in new stack
[Sep 22 18:03:55] VERBOSE¹⁹⁷⁶⁴[C-0000508f] pbx_builtins.c: Goto (default,8600056,1)
[Sep 22 18:03:55] VERBOSE¹⁹⁷⁶⁴[C-0000508f] pbx.c: Executing [8600056@default:1] Konference("SIP/MT001-00002391", "8600056,R") in new stack
[Sep 22 18:03:55] VERBOSE¹⁹⁶⁰⁵[C-000050a4] res_agi.c: <Local/5550142514002@default-00002903;1>AGI Script agi-VDAD_local_optimize.agi completed, returning 0
[Sep 22 18:03:55] VERBOSE¹⁹⁶⁰⁵[C-000050a4] pbx.c: Executing [138368@default:2] Wait("Local/5550142514002@default-00002903;1", "2") in new stack
[Sep 22 18:03:55] VERBOSE¹⁹⁶⁰⁶[C-0000508f] res_agi.c: <Local/5550142514002@default-00002903;2>AGI Script agi://127.0.0.1:4577/call_log--HVcauses--PRI-----NODEBUG-----16-----ANSWER-----17-----0-----SIP 200 OK) completed, returning 0
[Sep 22 18:03:56] VERBOSE¹⁹⁷⁶⁴[C-0000508f] res_rtp_asterisk.c: 0x7fb434000e00 -- Strict RTP learning complete - Locking on source address 185.101.180.186:51564
[Sep 22 18:18:32] VERBOSE²⁴⁴⁴⁶ manager.c: Manager 'sendcron' from 127.0.0.1, hanging up channel: SIP/MT001-00002391
[Sep 22 18:18:32] VERBOSE¹⁹⁷⁶⁴[C-0000508f] pbx.c: Executing [h@default:1] AGI") in new stack
[Sep 22 18:18:32] VERBOSE¹⁹⁷⁶⁴[C-0000508f] res_agi.c: <SIP/MT001-00002391>AGI Script agi://127.0.0.1:4577/call_log--HVcauses--PRI-----NODEBUG-----16--------------------SIP 200 OK) completed, returning 0
[Sep 22 18:18:32] NOTICE²⁴⁴⁴⁷ manager.c: Request to hangup non-existent channel: SIP/MT001-00002391

What can be the cause of the "hanging up channel" ?

Thanks in advance