Just sharing a similar experience about 2 years back.
I bought a used Nex 5N with SEL 50 lens. It was abt midnight when I met the gentleman/cheater in Eunos. During the meetup, he hurried me to check the camera, take picture and help me review the picture. It was late and the picture turn out ok on the white wall. I paid for it and left after 15 mins. When I reach home, I took out the lens to clean and realized there was a huge crack on the glass in front of the filter. On auto mode, the in camera processing took care of the line/shadow so everything looks ok. On A mode and other modes, every picture will show a dark line across the frame. I sms the seller within an hour and there was no reply. He replied the a few hours later, claim that there is no problem and it is dirty easily clean and asked me to meet him again the following night.
Guess what? When I met him, he took a look at the camera and said I tried to cheat him, that the camera is NOT the one he sold me haha. I left immediately, no point quarrelling.
I notice that these cheater do not usually post their actual nick. They will create a new nick, don't put their real name and prob give their wife or someone else's hp. Once transacted, u can never find them again if they don't answer the phone or someone says wrong number. anyway just sharing.