Investigate problem with websocket connection

[2021-03-16T15:29:07.837Z] | aiohttp.server | ERROR - Error handling request | X-Request-ID: 46a55f27-b3c4-4077-af45-a59b5386cbc8
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_protocol.py", line 418, in start
    resp = await task
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_app.py", line 458, in _handle
    resp = await handler(request)
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_middlewares.py", line 119, in impl
    return await handler(request)
  File "/usr/local/lib/python3.8/site-packages/prozorro_sale/tools/logging.py", line 66, in request_id_middleware
    response = await handler(request)
  File "/usr/local/lib/python3.8/site-packages/prozorro_sale/auth/__init__.py", line 107, in context_middleware
    return await handler(request)
  File "/usr/local/lib/python3.8/site-packages/prozorro_sale/auth/__init__.py", line 123, in handler
    return await func(request, *args, **kwargs)
  File "/procedure_mirror/procedure_mirror/main.py", line 39, in websocket_handler
    await request.app.mirror.sync_client(
  File "/usr/local/lib/python3.8/site-packages/mongodb_mirror/mirror.py", line 73, in sync_client
    if metric_ts := await client.get_last_timestamp():
  File "/usr/local/lib/python3.8/site-packages/mongodb_mirror/client.py", line 69, in get_last_timestamp
    response_data = await self.ws.receive_json()
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_ws.py", line 441, in receive_json
    data = await self.receive_str(timeout=timeout)
  File "/usr/local/lib/python3.8/site-packages/aiohttp/web_ws.py", line 426, in receive_str
    raise TypeError(
TypeError: Received message 8:1000 is not WSMsgType.TEXT