Not taking sides, but it is a pain when people use used parts and then blame the malfunction on the shop. Late last year, I had a repeat customer bring a used DVD player from his old vehicle for me to install in his dad's taxi. I had 2 vehicles ahead of him, but would be wrapped with them in like 5 minutes. So they showed me where the box was with the dvd player and told me everything was there. They were on a deadline, so as they were talking, I was knocking out on of the cars. They left. I get to the car and come to find out they didn't have the wiring harness to plug into the dvd player. I tried calling him and the dad. An hour goes by and he finally calls me back. So they come back by and come to find out he left it in the car, still installed, and the car is long gone. So the dad wanted to blame me because I was the "expert" for the harness not being there.