I sold a hard drive to a buyer in Spain for $55 + $18 shipping

The actual shipping is $35, I underestimated the shipping charge. I paid the extra cost.

Item was sold on Payment was received on Feb16th, and was shipped on 17th. I have a custom number showing item leaving US in a few days. But no tracking in spain.

On March 29th, I received an email from this buyer saying item does not work. This is like 42 days after the payment, if the shipping took 10 days, he still had the item for 30 days. I tested the item, it was working before I shipped it out.

I have given refund for 2 items within last month, in those cases I believed what the buyer was saying. But in this case I really have my doubt.