I did brakes on used cars at a dealer in the 90s. The weirdest thing I found was certain Ford trucks had bad heat treating or something in the rotors. I could resurface them and they were well within spec and after the were driven a short time they would pulsate and shake the steering wheel something fierce. I learned to just replace them, and they were the big 8 lug rotors. Had a lady who bought a used Ford come into the shop and yell at me about it before I knew the problem. All kinds of accusations were hurled. We did buy her new rotors but she was not happy. Probably still not happy.