Either it's been mishandled during shipping or after shipping.
I don't think you're liable personally, but as an incentive, you can offer buyer to help in insurance claim.
You can also say that it's been quite a while after it was shipped and who knows or who should really know what was happening with amp between date of delivery and over 10 days after, but instead you let insurance company say same thing and politely remove your personal liability.
P.S. I'm experienced retailer and sell vinyl records online and off the store front and dealing with cases like that almost on daily bases.
I don't think you're liable personally, but as an incentive, you can offer buyer to help in insurance claim.
You can also say that it's been quite a while after it was shipped and who knows or who should really know what was happening with amp between date of delivery and over 10 days after, but instead you let insurance company say same thing and politely remove your personal liability.
P.S. I'm experienced retailer and sell vinyl records online and off the store front and dealing with cases like that almost on daily bases.