Ununderstandible behaviour of data channel

[stserakhau]

Test scenario:

Chunk size 15kb.
For 200 files (avg 5 parallel downloads)

1. Open datachannel (line 1..5 below)
2. Transmit 5Mb file (sending chunks via channel.send(RTCDataChannelBuffer))
3. Close data channel (after receiving confirmation from receiver or by timeout (1 minute))

Result:
after ~100 successfully downloaded files I see next behaviour

After executing line 1..5 channel change state immediately to CLOSING -> CLOSED. State of the peerConnection = 'connected'

1. RTCDataChannelInit init = new RTCDataChannelInit();
2. init.priority = RTCPriorityType.VERY_LOW;
3. init.ordered = true;
4. RTCDataChannel fileChannel = rtcClient.peerConnection.createDataChannel(channelName, init);
5. fileChannel.registerObserver(new FileDownloaderRTCDataChannelObserver(fileChannel, fileResourceId, downloadStream));
6. 
7. class FileDownloaderRTCDataChannelObserver implements RTCDataChannelObserver {
8. ...
9.         @Override
10.         public void onStateChange() {
11.             File fileToTransmit = downloadStream.getFile();
12.             RTCDataChannelState state = fileChannel.getState();
13.             switch (state) {
14.                 case OPEN -> {
15.                     log.info("File download channel opened: {}", fileChannel.getLabel());
16.                     .......
17.                 }
18.                 case CLOSED -> {
19.                     log.info("File download channel closed: {}", fileChannel.getLabel());
20.                     ...
21.                 }
22.             }
23.         }
24. ...
25. }

Expected behaviour:
Channel should not closed after creation.

• OS: Intel(R) Core(TM) i7-5820K CPU @ 3.30GHz, 12 cores, 31G, Windows 10 , 64 bit Build 19041 (10.0.19041.2364)
• JRE version: Java(TM) SE Runtime Environment (17.0.2+8) (build 17.0.2+8-LTS-86)
• webrtc 0.7.0
• spring-boot 2.7.5

Additional context

1. After reconnecting peer client (refresh page in browser) data channel beginning to work.
2. Some strange on the Ethernet graphic in Task manager
   I see execution of the code below in debug mode

     RTCDataChannelBuffer channelBuffer = new RTCDataChannelBuffer(byteBuffer, true);
     channel.send(channelBuffer);

But I don't see the network traffic. states of peer connection = connected, channel = open (When file transmittion is active this line generates traffic 10-15 mbits)