Never get into a back and forth exchange like that with a buyer. It leads to nowhere. When a problem arises, just say “return for refund.” Although you have chosen No Returns, as is your right, in practice there is really no such thing on eBay. A determined buyer can easily claim Not As Described to overrule that choice. With some kind of return policy, it is much less tempting for a buyer to open a bogus NAD case.
You sell sensitive equipment that requires certain temperatures for functioning and very careful handling, yet you did not even consider that the item indeed may have failed due to improper care while in transit. Since you dropped it off at a third-party shipping site, you have no way of knowing how your package was dealt with before it ever changed hands with the USPS.
It is perfectly credible that the unit was ruined by the time it reached the buyer. Even more so if the package was being boxed up at the first location and then handed over to the postal carrier. The buyer may have been telling the truth. But immediately jumping to the conclusion that the buyer was perpetrating a fraudulent claim prevented proper investigation in finding out what happened. It appears the buyer is guilty of the same mistake, jumping to a conclusion that you were doing the same.
At the point the buyer reported the problem, it would have been better to request they save all packing material in preparation for you to file on the Priority insurance available to eBay sellers. Did you take out additional shipping insurance to protect your interests in case of damage? If so, there is no need for back-and-forth heated exchanges. You simply advise the buyer they will be refunded in full and you file the insurance online. The buyer gets refunded and the PO makes you whole. End of story.
While it is unfortunate that the buyer made an unfounded accusation, it is the seller’s job to remain professional and not get into a name calling, **bleep**-for-tat, devolving exchange. You essentially called him a liar and a scam artist. He accused you of deliberately selling him faulty merchandise. None of that solved the problem and only made matters worse.
“Return for refund“ is the only exchange that makes sense on a platform where the buyer’s interests always come first. It is the best way to deal with a dissatisfied customer. And while it matters in the real world, on eBay it doesn't matter if the buyer is being truthful or making up a story to force a return. The end result is the seller can get hung out to dry. Sellers have to look after their own interests, eBay will not. Here, it is not about fair play or principals, it is about protecting one’s selling account from defects and lowered seller metrics. Ebay will side with the buyer. The seller must know how this game is played.
