First of all, i wan to clarify that i am not standing on any side.
From wat I understand, it seems like WONG has done wat he can do. But AE76 is not. AE76, u need to show some proofs about ur complaints. You cant jx simply claim the goods is not in the condition it should be and refuse to clear the outstanding.
As a recipient, u need to play ur part too. If u find the goods has signs of opened or unseal beforehand. Do not sign / receive the item. Reject it when it delivered to ur doorstep, and open it in front of post office personnel in post office. Quest the post office personnel, instead of the sender. Bear in mind, post office will not receive any parcel (box) or documents in unsealed or broken condition. It must be something happened while the goods on the way to ur doorstep. U should claim the goods value from post office, not from WONG.
If AE76 received the goods (box) in good condition, no sign of opened or unsealed. But the item does not work well / faulty, then only WONG should be responsible for that.