Sold an item new, now buyer claims "item not a described"?

Buyer received item and opens a "not as described" case because apparently, the item is now mysteriously cracked along the back-side. Buyer says box was well packaged and intact. It also had additional protection from it's own product box. I used a combination of airbags, confetti and brown shipping paper all stuffed in there. No way it could be damaged during shipment with all the packing I did.

I asked the buyer to send me pictures which they finally did after asking a second time. The pictures show the damage, but I'm also seeing scuffs along with the cracks that weren't there when I shipped the item. Buyer didn't show me pictures of the packaging though. It was also insured, but the buyer refuses to cooperate and file a claim with the post office. All the buyer wants is a full refund.

And I'm not sure if I can take out the claim because I don't have the item back in my hands. And even if I have the buyer ship the item back to me, how do I know the PO will honor a claim since it's being put back into the mail system a second time?

I'm suspicious of the buyer because they don't want to file a claim. It makes me wonder if this is a scam. Buyers purchase brand new item, receive it, switch out new item for old, file item not as described, get full refund plus free item. I'm out of an expensive item plus a sale.

What do I do now?