ERROR: There is an active agent....

[migrau]

After days running without problems, and pretty randomly (1-2 days per week):

0:07:11.432 TRACE- websocket session 'Ny7pCA8oghIBNF8vu0wMB9A592E='
00:07:11.468 INFO - Received heartbeat
00:07:56.433 INFO - Sending heartbeat
00:07:56.433 TRACE- websocket session 'Ny7pCA8oghIBNF8vu0wMB9A592E='
00:07:56.469 INFO - Received heartbeat
00:08:41.433 INFO - Sending heartbeat
00:08:41.433 TRACE- websocket session 'Ny7pCA8oghIBNF8vu0wMB9A592E='
00:08:41.469 INFO - Received heartbeat
00:09:26.434 INFO - Sending heartbeat
00:09:26.434 TRACE- websocket session 'Ny7pCA8oghIBNF8vu0wMB9A592E='
00:10:11.434 INFO - Sending heartbeat
00:10:11.434 TRACE- websocket session 'Ny7pCA8oghIBNF8vu0wMB9A592E='
00:10:56.434 INFO - Sending heartbeat
00:10:56.435 TRACE- websocket session 'Ny7pCA8oghIBNF8vu0wMB9A592E='
00:11:41.435 INFO - Sending heartbeat
00:11:41.435 TRACE- websocket session 'Ny7pCA8oghIBNF8vu0wMB9A592E='
00:12:26.436 INFO - Sending heartbeat
00:12:26.436 TRACE- websocket session 'Ny7pCA8oghIBNF8vu0wMB9A592E='
00:13:11.436 INFO - Sending heartbeat
00:13:11.436 TRACE- websocket session 'Ny7pCA8oghIBNF8vu0wMB9A592E='
00:13:28.686 INFO - Closed for unknown reason after
00:13:28.686 INFO - Session duration 0d 0h 21m 48s
00:13:31.417 INFO - Connecting to Tower
00:13:31.558 INFO - Connection to Tower established
00:13:31.558 DEBUG- Websocket session URL: https://api.tower.nf/agent/a4c58637-0036-4584-9e63-ab0c128eefc6/connect
00:13:31.561 ERROR- There is an active agent for this user and connection ID. Please close it before starting a new one.

Not sure why it happens...
Thanks!