Stock rotation blunder perhaps? New stock arrives, gets warehoused with the older stock (lets say cartons on top or in front) and it gets sent out first, leaving the old stuff to continue to date.

In *any* case - poor stocktaking & sales skills are obvious, and seems they need it brought to their attention, so they get their act together pronto! (Do they still have reps calling in, or has that also gone by the wayside?)