I am seeing a new warning in the logs that I think has just started recently:
[W 2022-06-06 23:16:47.436 ServerApp] Got events for closed stream <zmq.eventloop.zmqstream.ZMQStream object at 0x000000000>
The 0x000000000 is different each time.
Any idea what may be causing this, and how it can be corrected?