You should have detailed close-up photographs of the drone before you sold it. There is no history of cracks just happening.
You'll probable just have to work out a deal with the buyer and follow eBay policy.
Actually, flying fixed wing single engine planes is not that simple as you have control of multiple parameters. If you pull back the stick/yoke you change the angle of attack and slow the airplane and descent, as in the flare when you land or...
Who was the actual seller? Was it Amazon.com or a reseller selling products on Amazon? Did you try to actually contact the reseller and explain the problem? If the seller was selling stolen property, then you recourse should be through the...
Probably not now, but at one time this was a serious concern. People traveling to places like Hong Kong would buy camera equipment at greatly discounted prices, similar to DJI drones today, and be forced to pay import duties on the items upon...