DTLS alert after DTLS esteblished

Hi
I use janus with sip plugin to call for users on custom mobile phone app.
On some calls I have DTLS alert after DTLS have been established.
I don’t know where I can find a reason.
It would be nice if you can guide me.

[Sat Aug 19 14:26:08 2023] [7817236608466597] Remote SDP:
[Sat Aug 19 14:26:08 2023] [7817236608466597] There are 1 audio, 0 video and 0 data m-lines
[Sat Aug 19 14:26:08 2023] [7817236608466597] Parsing m-line #0
[Sat Aug 19 14:26:08 2023] [7817236608466597] ICE ufrag (local): FGiJ
[Sat Aug 19 14:26:08 2023] [7817236608466597] ICE pwd (local): O42OVvq18DDJRdKfKdi47NII
[Sat Aug 19 14:26:08 2023] [7817236608466597] Fingerprint (local) : sha-256 9F:C1:33:E5:58:8B:13:AC:D1:A1:49:1B:E0:D8:8A:43:89:23:7C:07:77:3B:A4:E8:23:F0:21:89:DD:17:37:28
[Sat Aug 19 14:26:08 2023] [7817236608466597] DTLS setup (local): active
[Sat Aug 19 14:26:08 2023] [7817236608466597] Setting accept state (DTLS server)
[Sat Aug 19 14:26:08 2023] [7817236608466597] Setting remote credentials…
[Sat Aug 19 14:26:08 2023] [7817236608466597] Peer audio SSRC: 538529435
[Sat Aug 19 14:26:08 2023] [7817236608466597] – ICE Trickling is supported by the browser, waiting for remote candidates…
[Sat Aug 19 14:26:08 2023] [7817236608466597] Sending event to transport…
[Sat Aug 19 14:26:09 2023] [7817236608466597] Discovered new remote candidate for component 1 in stream 1: type=prflx
[Sat Aug 19 14:26:09 2023] [7817236608466597] Stream #1, Component #1
[Sat Aug 19 14:26:09 2023] [7817236608466597] Address: 217.76.76.222:30679
[Sat Aug 19 14:26:09 2023] [7817236608466597] Priority: 1853824767
[Sat Aug 19 14:26:09 2023] [7817236608466597] Foundation: remote1
[Sat Aug 19 14:26:09 2023] [7817236608466597] Adding remote candidate component:1 stream:1 type:prflx 217.76.76.222:30679 → 217.76.76.222:30679
[Sat Aug 19 14:26:09 2023] [7817236608466597] Transport: UDP
[Sat Aug 19 14:26:09 2023] [7817236608466597] Candidate added to the list! (1 elements for 1/1)
[Sat Aug 19 14:26:09 2023] [7817236608466597] ICE already started for this component, setting candidates we have up to now
[Sat Aug 19 14:26:09 2023] [7817236608466597] ## Setting remote candidates: stream 1, component 1 (1 in the list)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Queueing candidate 0x7f069401aa10 (startup)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Component state changed for component 1 in stream 1: 2 (connecting)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Processing candidate 0x7f069401aa10
[Sat Aug 19 14:26:09 2023] [7817236608466597] 1 remote candidate added
[Sat Aug 19 14:26:09 2023] {“session_id”:2702106224871374,“handle_id”:7817236608466597,“candidate”:{“sdpMLineIndex”:0,“sdpMid”:“0”,“candidate”:“candidate:2964996237 1 udp 1686052607 217.76.76.222 22520 typ srflx raddr 0.0.0.0 rport 0 generation 0 ufrag FGiJ network-id 3 network-cost 900”},“janus”:“trickle”,“transaction”:“H6JAtkcYOA5m”}
[Sat Aug 19 14:26:09 2023] [7817236608466597] Trickle candidate (0): candidate:2964996237 1 udp 1686052607 217.76.76.222 22520 typ srflx raddr 0.0.0.0 rport 0 generation 0 ufrag FGiJ network-id 3 network-cost 900
[Sat Aug 19 14:26:09 2023] [7817236608466597] Adding remote candidate component:1 stream:1 type:srflx 0.0.0.0:0 → 217.76.76.222:22520
[Sat Aug 19 14:26:09 2023] [7817236608466597] Transport: UDP
[Sat Aug 19 14:26:09 2023] [7817236608466597] Candidate added to the list! (2 elements for 1/1)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Queueing candidate 0x7f069401add0
[Sat Aug 19 14:26:09 2023] [7817236608466597] Processing candidate 0x7f069401add0
[Sat Aug 19 14:26:09 2023] [7817236608466597] 1 remote candidate added
[Sat Aug 19 14:26:09 2023] [7817236608466597] Looks like DTLS!
[Sat Aug 19 14:26:09 2023] [7817236608466597] New selected pair for component 1 in stream 1: 2 ↔ remote1
[Sat Aug 19 14:26:09 2023] [7817236608466597] Component is ready enough, starting DTLS handshake…
[Sat Aug 19 14:26:09 2023] [7817236608466597] Component state changed for component 1 in stream 1: 3 (connected)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Component state changed for component 1 in stream 1: 4 (ready)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Creating retransmission timer with ID 7
[Sat Aug 19 14:26:09 2023] {“session_id”:2702106224871374,“handle_id”:7817236608466597,“candidate”:{“sdpMLineIndex”:0,“sdpMid”:“0”,“candidate”:“candidate:2964996237 1 udp 1686052607 217.76.76.222 63816 typ srflx raddr 0.0.0.0 rport 0 generation 0 ufrag FGiJ network-id 3 network-cost 900”},“janus”:“trickle”,“transaction”:“N4ODhxdMh4TB”}
[Sat Aug 19 14:26:09 2023] [7817236608466597] Trickle candidate (0): candidate:2964996237 1 udp 1686052607 217.76.76.222 63816 typ srflx raddr 0.0.0.0 rport 0 generation 0 ufrag FGiJ network-id 3 network-cost 900
[Sat Aug 19 14:26:09 2023] [7817236608466597] Adding remote candidate component:1 stream:1 type:srflx 0.0.0.0:0 → 217.76.76.222:63816
[Sat Aug 19 14:26:09 2023] [7817236608466597] Transport: UDP
[Sat Aug 19 14:26:09 2023] [7817236608466597] Candidate added to the list! (3 elements for 1/1)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Queueing candidate 0x7f069401ae70
[Sat Aug 19 14:26:09 2023] [7817236608466597] Processing candidate 0x7f069401ae70
[Sat Aug 19 14:26:09 2023] [7817236608466597] 1 remote candidate added
[Sat Aug 19 14:26:09 2023] [7817236608466597] Looks like DTLS!
[Sat Aug 19 14:26:09 2023] [7817236608466597] Written 153 bytes on the read BIO…
[Sat Aug 19 14:26:09 2023] [7817236608466597] >> >> … and sent 695 of those bytes on the socket
[Sat Aug 19 14:26:09 2023] [7817236608466597] … and read -1 of them from SSL…
[Sat Aug 19 14:26:09 2023] [7817236608466597] Initialization not finished yet…
[Sat Aug 19 14:26:09 2023] [7817236608466597] DTLSv1_get_timeout: 983
[Sat Aug 19 14:26:09 2023] [7817236608466597] Looks like DTLS!
[Sat Aug 19 14:26:09 2023] [7817236608466597] Written 579 bytes on the read BIO…
[Sat Aug 19 14:26:09 2023] [7817236608466597] >> >> … and sent 554 of those bytes on the socket
[Sat Aug 19 14:26:09 2023] [7817236608466597] … and read -1 of them from SSL…
[Sat Aug 19 14:26:09 2023] [7817236608466597] DTLS established, yay!
[Sat Aug 19 14:26:09 2023] [7817236608466597] Computing sha-256 fingerprint of remote certificate…
[Sat Aug 19 14:26:09 2023] [7817236608466597] Remote fingerprint (sha-256) of the client is 9F:C1:33:E5:58:8B:13:AC:D1:A1:49:1B:E0:D8:8A:43:89:23:7C:07:77:3B:A4:E8:23:F0:21:89:DD:17:37:28
[Sat Aug 19 14:26:09 2023] [7817236608466597] Fingerprint is a match!
[Sat Aug 19 14:26:09 2023] [7817236608466597] SRTP_AES128_CM_SHA1_80
[Sat Aug 19 14:26:09 2023] [7817236608466597] Key/Salt/Master: 30/16/14
[Sat Aug 19 14:26:09 2023] [7817236608466597] Created inbound SRTP session for component 1 in stream 1
[Sat Aug 19 14:26:09 2023] [7817236608466597] Created outbound SRTP session for component 1 in stream 1
[Sat Aug 19 14:26:09 2023] [7817236608466597] The DTLS handshake for the component 1 in stream 1 has been completed
[Sat Aug 19 14:26:09 2023] [7817236608466597] The DTLS handshake has been completed
[Sat Aug 19 14:26:09 2023] [7817236608466597] Telling the plugin about it (JANUS SIP plugin)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Sending event to transport…; 0x7f0704002040
[Sat Aug 19 14:26:09 2023] [7817236608466597] DTLS already set up, disabling retransmission timer!
[Sat Aug 19 14:26:09 2023] [7817236608466597] Notifying that we are receiving audio on mid 0
[Sat Aug 19 14:26:09 2023] [7817236608466597] Sending event to transport…
[Sat Aug 19 14:26:09 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:09 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:10 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:10 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:11 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:11 2023] [7817236608466597] Got an RTCP packet
[Sat Aug 19 14:26:11 2023] [7817236608466597] Got audio RTCP (32 bytes)
[Sat Aug 19 14:26:11 2023] [7817236608466597] Got an RTCP packet
[Sat Aug 19 14:26:11 2023] [7817236608466597] Got audio RTCP (56 bytes)
[Sat Aug 19 14:26:11 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:12 2023] [7817236608466597] Fixing SSRCs (local 1903073, peer 538529435)
[Sat Aug 19 14:26:12 2023] [7817236608466597] Got an RTCP packet
[Sat Aug 19 14:26:12 2023] [7817236608466597] Got RTCP BYE on stream 1 (component 1)
[Sat Aug 19 14:26:12 2023] [7817236608466597] Got audio RTCP (44 bytes)
[Sat Aug 19 14:26:12 2023] [7817236608466597] Looks like DTLS!
[Sat Aug 19 14:26:12 2023] [7817236608466597] Written 39 bytes on the read BIO…
[Sat Aug 19 14:26:12 2023] [7817236608466597] DTLS alert triggered on stream 1 (component 1), closing…
[Sat Aug 19 14:26:12 2023] [7817236608466597] Hanging up PeerConnection because of a DTLS alert
[Sat Aug 19 14:26:12 2023] [7817236608466597] … and read 0 of them from SSL…
[Sat Aug 19 14:26:12 2023] [7817236608466597] Any data available?
[Sat Aug 19 14:26:12 2023] [7817236608466597] >> >> … and sent 39 of those bytes on the socket
[Sat Aug 19 14:26:12 2023] [7817236608466597] DTLS alert triggered on stream 1 (component 1), closing…
[Sat Aug 19 14:26:12 2023] [7817236608466597] Telling the plugin about the hangup (JANUS SIP plugin)
[Sat Aug 19 14:26:12 2023] [7817236608466597] Sending event to transport…
[Sat Aug 19 14:26:12 2023] [7817236608466597] Removing stream 1 from agent 0x7f06a000f430
[Sat Aug 19 14:26:12 2023] [7817236608466597] Closing nice agent 0x7f06a000f430
[Sat Aug 19 14:26:12 2023] [7817236608466597] Notifying WebRTC hangup; 0x7f0704002040
[Sat Aug 19 14:26:12 2023] [7817236608466597] Sending event to transport…; 0x7f0704002040
[Sat Aug 19 14:26:12 2023] [7817236608466597] WebRTC resources freed; 0x7f0704002040 0x7f07040060a0

The endpoint is closing the connection. Why that happens you should go and check: Janus is simply reacting to that.