Tell me about your experience of being scammed when buying a used car?

After buying it back, all the procedures went smoothly and there was no sign that it was a mortgaged car. This friend happily drove the car for more than half a year. One day when I met him during the weekend, he pulled me and said something he regretted in a very tangled voice, "Why do some people say that my car has been spray-painted? It rained for several days in a row and I found that there was still paint on the A-pillar. It's leaking! Brother, you are in the automobile industry, please help me find out what's going on." So I was dragged by him to take a closer look at the Elantra. After looking at it, I found that the paint on this car was completely gone, and it took a long time to spray paint, because some places had started to peel. When I opened the spare tire cover in the trunk, I found that the bottom of the trunk of this car had been replaced, which meant that it had been severely dragged across the bottom and then cut off and re-welded. There were four tires of four brands with different degrees of tread friction marks. At this time, my friend was about to cry. I told him that these were not serious. Let’s take a look inside. I got into the car and opened the left door rubber strip to see the color inside. It turned out to be blue, like the color of a taxi. In other words, the door has been replaced, which is a bit serious. The airbag malfunction sign was displayed on the instrument panel. When I asked him, he said it wasn't there when I bought it, but it popped up recently. It is basically concluded that this is a car that has been in a serious accident. After I told him, he was helpless and angry, and claimed that he wanted to sell it.