Tickets reprinted after being scanned

I've searched for some info on this but haven't found an instance of this.  We had some tickets get printed then scanned when the patrons attended.  Then, for whatever reason, the tickets were reprinted and scanned again even though they had already been scanned.

I can see special cases where we may need to reprint tickets that have been scanned already, but is there a setting somewhere than can prevent this from happening?  Or is it just a case of sloppy box office work to reprint tickets when someone had already scanned them?

Thanks!

RJ