When you buy things for repair from the internet, it’s always a gamble. One must never assume that the former owner is stupid and didn’t try everything he could, to make it work. Some people are more skilled than others. Maybe one product is OK and it was a matter of not knowing how to use it, that’s a lucky one. Maybe it’s a minor defect and they didn’t bother to try to fix it anymore. And, there can be unfortunate events where the product is badly and complicatedly damaged, and there’s nothing you can do, or it’s not economically feasible to fix it.