Some modules take several minutes to activate a service and they don't create a lock of any sort when starting activating to prevent another process, be it cron or human, from duplicating the action.
I've seen multiple instances of an order getting entered, a staffer clicking "activate" on the service to go ahead and provision it and either the cron was already running, or starts running while the staff-induced activation is still running and two services are setup, two activation emails are sent, but only one record exists in blesta so you end up with a totally orphaned service.
A simple fix for this is to use locks in the database during provisioning.