bealine wrote :
The "Departures Control System" will not allow the same tag number to be printed twice (until the numbers have been round the clock!)
Depending on the DCS system in use, the following is more correct :
The "Departures Control System" should not allow the same tag number to be printed twice (until the numbers have been round the clock!)
With some systems, it is quite possible to reprint a bagtag either by mistake or on purpose. Either that, or it is human error as you say.