A customer opens a brand-new order and finds somebody else's used item inside. Trace it back through your returns process and tell me where it went wrong.
Almost always the unit was restocked as sellable on receipt, before anyone graded it. Receipt and grading are different events with different owners, and the returned unit must sit in a non-sellable location until a disposition decision has been made and recorded. Use this returns grading answer to show the decision, trade-off, and evidence rather than a memorised definition.