If two reloads of the flow monitor happens at the same time, It will stop the service.
You can reproduce this with a single user logged in:
1) Leave "Automatic Refresh Interval" at a set period of seconds, such as 5 seconds.
2) Manually reload the flow monitor before It happens automatic by the refresh interval set.
The Pktcapd service will stop, and the flow monitor will stop working too.
Thanks!