Ouch! Yeah I really don't understand the science as to why these fail but there's just so many instances of them failing. It's not even the molex end that fails, but the sata end. So I don't understand it really, it just is a thing. I thought maybe the sata standard had some kind of sense line that is bypassed and maybe it delivers too much voltage or something, but I checked the spec and there is no such pin. Something about the molding process of the sata connector, but still does not explain why it's only the adapters that fail and not the factory ones, that use the same molded ends.
I was so tempted to just use one of the cables made for another PSU and just check to make sure the pin out matches but sata cables are kinda hard to probe with the multimeter.
I might have to cannibalize an old hard drive so I can make a tester. Basically need a circuit that detects the voltage and lights up a LED if it's within range. This would allow to repurpose PSU cables on different PSUs by testing that the pin out is correct.