[otrs] Ticket reminders for closed tickets

Hi, Our system (2.4.5) is generating daily reminder emails for tickets that are closed - it appears to do this only for tickets that have been in the 'pending reminder' state and have been closed without going back to the 'open' state. Re-opening the tickets and closing them again doesn't appear to clear the problem. I can't find any reference to this anywhere except one old ticket in Bugzilla that has been marked as invalid, so presumably it's a configuration problem. Any suggestions gratefully received. Regards, John