Buyer says item is not working but didn't check themselves before sending it off to have it calibrat

[mosesramone]

I sold a used electronic item with it needs calibration in the description, they have now asked for a refund just over a week after receiving. I ensured that it was fully working before shipping it to them.

They are  saying the item is damaged and would like a refund but admit they didn't try to turn it on and use the equipment themselves they immediately sent it off to have it calibrated and the 'expert' is saying it doesn't work. 

I would understand if they tested it themselves first but now there is no way of telling when damage could have occurred. 

How do I move forward with this?

[kensgiftshop]

If they haven't filed an INAD yet, tell them to return it for a refund.

If they have filed an INAD and you want it returned before refunding, accept the return and provide return shipping.

[mosesramone]

Thanks

How can I tell if they have filed for a INAD?

What if the person they sent it to damaged the item. It means I will have an item I cannot sell again and I lose out.