Hi, Sometimes, lava master will show next error, then seems zemomq crash, do you know what's the potential cause?

2019-08-20 09:14:39,576   DEBUG lava-worker-1 => PING(20)
2019-08-20 09:14:39,578   DEBUG lava-worker-2 => PING(20)
2019-08-20 09:14:39,580   DEBUG lava-worker-3 => PING(20)
2019-08-20 09:14:44,467   ERROR [CLOSE] Unknown exception raised, leaving!
2019-08-20 09:14:44,467   ERROR 'utf-8' codec can't decode byte 0xc0 in position 10: invalid start byte
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/lava_server/management/commands/lava-master.py", line 687, in handle
    self.main_loop(options)
  File "/usr/lib/python3/dist-packages/lava_server/management/commands/lava-master.py", line 731, in main_loop
    while self.controler_socket():  # Unqueue all pending messages
  File "/usr/lib/python3/dist-packages/lava_server/management/commands/lava-master.py", line 234, in controler_socket
    hostname = u(msg[0])
  File "/usr/lib/python3/dist-packages/zmq/utils/strtypes.py", line 34, in cast_unicode
    return s.decode(encoding, errors)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xc0 in position 10: invalid start byte
2019-08-20 09:14:44,467    INFO [CLOSE] Closing the controler socket and dropping messages