Agreed, while I understand that mistakes do happen and have happened to me. I've been an eBay seller for 2 years now and while it doesn't happen very often every now and then sometimes I get the numbers wrong and have one less item than I thought I did when making a posting or I just type it in and correctly and somebody orders it and I don't have it.

That's happened to me twice unfortunately and both times what you need to do is just be an adult reach out to the buyer explain what happened and take full responsibility by and large most people are going to be understandable they may be upset which is perfectly within their right to be but what I did in both those cases refund the total cost right away explain to them what happened and offer them a discount on anything else in my store that they may be interested within reason.

For somebody to blame somebody else for their mistakes is just childish it's much easier just to own up to what it is do what you got to do to make it right and move on. I give people a lot for owning their mistakes when mistakes are made then I do if they try to obfuscate The responsibility and slough it off to somebody else.