I have had similar results with the odd spare tool or other gear without moving parts.
But, since 2010 or so, I have rebuilt regulators for friends or clients, all purchased off of eBay, as either "fully functional" or "due for an annual;" and about twenty percent of those were absolutely irredeemable -- so damaged were the sealing surfaces of the first stages, from either cross-threading (I can't imagine how) or simply ham-fisted o-ring removal, that a reliable and steady IP was impossible. Second stages frequently had bent -- useless -- servo valves; stripped screws; or rotted diaphragms.
The rodent damage on this thread was a first for me; and it still hangs on my wall of shame.
Some items were easily returned; others required lengthy fights over PayPal; and still others -- as illustrated in this thread -- were foreigners with fake US addresses, whom eBay had little interest in pursuing; and who, otherwise, fell into legal gray areas. All, by the way, possessed stellar reviews; and oddly, the resultant poor reviews from my friends and clients, particularly for "Power-Sellers" frequently went missing from their later profiles.
Now, the site even requires a seven day waiting period, in order to post a negative review, for some "privileged" eBay clients:
"If the seller is a power seller then it is an eBay requirement that less than positive feedback cannot be left for seven days. You are to use this time to allow the seller to try and solve your problem. If they do not solve your problem then you are free to leave your feedback after sever full days have elapsed . . ."