I wonder what people's experience of selling used goods in Cambodia is like?

About a year ago I sold a good quality and still reasonably new laptop to a Khmer. I allowed him plenty of time to give it a thorough check-over before he decided to take it. He ended up taking only about 5 minutes and I encouraged him to take his time and check it more but he said it was ok, paid for it and left. He then messaged me later that evening to say that the right shift key didn't work. My first thought was 'who the hell uses the right shift key?' and I gave him plenty of support to try to resolve the issue but he still claimed that it didn't work. I have honestly never used the right shift key so it's not something I would have been aware of if it wasn't working, but it did cross my mind that of all the keys to fail, it seems strange that it was only one, and not only that, but one of the least used ones, as far as I'm aware. (no doubt this is where everyone jumps in to tell me the right shift key is the most used key on the entire keyboard)

I decided that as I'd sold it while it was still in warranty, along with the original receipt, and I had given him plenty of time to check it, that I had done nothing wrong and didn't offer a refund. Even stores don't offer refunds here. Why should someone who had sold something used? In my country there's such a thing as 'sold as seen', and I knew that I hadn't deliberately ripped him off.

Anyway, today I sold a used gaming keyboard and lo-and-behold, despite taking my own laptop when I met him to allow him to give it a thorough check before purchase, which he did for only a few minutes, and again, I encouraged him to check it further and take his time, he's now messaged me to say that the right 'alt' key doesn't work. Again - who the hell used the right 'alt' key? I certainly don't so again, I admit that it's not something I'd check, but it seems a bit fishy that again, it's only one key that doesn't work and it's one of the least used keys on the keyboard.

I have given him plenty of support to try to get it working - maybe it's set to the wrong language, try it on a different device, check the drivers, update windows etc... but still he claims it's not working. What does he want me to do? Again it's in warranty and sold with the original receipt. so I am taking the 'sold as seen' stance again on this one. If it genuinely is faulty, I do feel a bit bad as no-one likes to be sold a dud. Note to everyone - always thoroughly check used goods!

But it does seem like a bit of a strange coincidence that almost identical issues have occurred, where only one single key is apparently faulty and it's a key that a seller is unlikely to check before selling.

A ruse to get some sort of discount or money back, or just coincidence?

Anyone else sell used items here? Any issues like this?