How bad is the USPS?

I shipped a carb via USPS to a guy in PA a few years ago. He said the package and carb was damaged. He sent the carb back and I refunded his cash.

When I got the carb back (AFB) I found he stripped the carb of parts which he likely needed and sent back the shell. USPS didn't even try to help... not sure what they would have done anyway. Yes it was insured but the buyer never filed a claim.

I used to manufacture ash door reinforcements for Triumph TR2 and TR3 cars. I had so much difficulty getting those parts delivered to Europe that I stopped making them. I could ship them UPS or Fedex but no one wanted to pay the rate. Shipping via the postal service meant a 75% chance the Euro post offices never made the delivery. Great Britain, Italy and France were the worst. But I did have one buyer in Germany who claimed to never have gotten the parts yet the post office sez they tried three deliveries before they sent the parts back to me.