Should I give my buyer a full refund on a prop?

[ToadServant]

Hello, I would like to hear the opinion from a more unbiased point of view on an issue I have with an eBay sale.

This is the prop I sold. https://www.ebay.com/itm/374000174059 or it is a Mercury Performance Cleaver Prop 14 X 22P 48-75770-22

The buyer feels that I should refund him 100% and that he shares no blame in the transaction. I would enjoy hearing your perspective on this issue, I would like to be fair to my buyer, so if this is 100% my fault as he claims, I think I owe him all of his money back. I got this particular prop from R&R prop in las vegas after it closed down.

Situation:
Buyers message paraphrased.
Someone thinned the blades on the prop I sold him and I didn't disclose this. He claims the blades are about 1mm, or 0.040" just back of the leading edge. (see attached picture provided by buyer) He said when he tried to set the leading edges equal, one of the blades cracked. He says he has a garage operated prop shop where he designs racing props. He claims I advertised the prop in good condition, but an excessively thinned prop is not in good condition because it will not last long.


I'm going to leave out my point of view on this to keep this fair.

So far, I accepted his return and offered him 2/3s of his money back.