core: Detected blocking call to sleep inside the event loop

The problem

I am running HA Core in a Docker container. Whenever I restart, I get the following message:

2022-03-29 15:38:09 ERROR (bellows.thread_0) [homeassistant] Error doing job: Exception in callback SerialTransport._call_connection_lost(None)
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/asyncio/events.py", line 80, in _run
    self._context.run(self._callback, *self._args)
  File "/usr/local/lib/python3.9/site-packages/serial_asyncio/__init__.py", line 417, in _call_connection_lost
    self._serial.close()
  File "/usr/local/lib/python3.9/site-packages/serial/urlhandler/protocol_socket.py", line 104, in close
    time.sleep(0.3)
  File "/usr/src/homeassistant/homeassistant/util/async_.py", line 173, in protected_loop_func
    check_loop(func, strict=strict)
  File "/usr/src/homeassistant/homeassistant/util/async_.py", line 135, in check_loop
    raise RuntimeError(
RuntimeError: Detected blocking call to sleep inside the event loop. This is causing stability issues. Please report issue
[finish] process exit code 0

What version of Home Assistant Core has the issue?

2022.3.5

What was the last working version of Home Assistant Core?

No response

What type of installation are you running?

Home Assistant Container

Integration causing the issue

I cannot tell. Too new.

Link to integration documentation on our website

No response

Diagnostics information

It is not clear to me from the message which integration is causing the problem. Any clues?

Example YAML snippet

No response

Anything in the logs that might be useful for us?

No response

Additional information

I really need some pointers in how to figure out the best information you need to help me.