The reason it is the buyer who has to claim for damage is that they have the item and the packaging, the only way the sender could claim would be if the buyer returned the item with the packaging and assigned the right to claim over to the sender.

If you send a replacement and then the buyer goes on to claim from AP then it hasn't cost you anything so it is AP's problem, not yours and if the item was correctly packaged the buyer will have no chance of getting anything from AP.

Have to ask, how do you keep items dry when you are packing them underwater?:|