О нерадивой замене колодок — Toyota Chaser, 2.5 л., 1998 года на DRIVE2

I was returning home a couple of days ago and noticed a strange thing: when braking from a speed of more than one hundred kilometers, a hum and strong vibration appear in the left right wheel.
Well, somehow my wife and I got to the house, I go out - the wheel is all black, the disc is in some kind of black coating both inside and out, the heat from it comes down like a kick-ass. What to do, Friday, evening, almost all services are closed. Found a round-the-clock, drove in, lifted the car. It turned out that the upper piston was stuck in the caliper. They removed and cleaned both the piston and its cylinder.
It turned out that this could be if, when replacing the pads, they were not checked, cleaned and lubricated. More precisely, everyone does it, but for some reason with one of them, and the second they score.
Thank God that was the problem.