The seller of the boxes could fix this by putting an outer wrapping on the boxes to which they affix the label so that there was no way for the label to stay on the box.
This will lead to the inventory of granola to be out of sync with the actual amount at the warehouse, but in that case I'm assuming Amazon would eat the cost since they're the ones that "lost" the missing inventory. Think about a physical store. If they lose some of their inventory, it's the store's problem, not the product's.
To me it seems... far from certain that Amazon would attribute the inventory errors and customer complaints correctly.
From the perspective of Amazon's system they're mailing out The Packaging Wholesalers' sealed box, customers are saying it has the wrong item in, therefore The Packaging Wholesalers must be unreliable chumps that can't pack a box correctly.