Korganizer delete difficulty

I have set akonadi up to use an ics file as a compatibility resource. This seems to be the proper way to do it. All my todos, appointments and birthdays and their associated reminder alarms all work as they should. However, when I complete a todo or an appointment has passed and I wish to delete it from my calendar, regardless of whether I choose delete or archive to a file, upon restarting korganizer, the deleted entries are back! I cannot get rid of them. Is this a known bug or have I set something up wrong?