I had a smoking and bad-brake-smelling L front wheel this summer coming down steep mountain slopes. I thought the car might light on fire. I went to brake and the brakes mostly failed. When a shop heard the story and pulled the wheel off, he pointed to a piece of metal dragging on the neck of the rotor and said the pads had been put in wrong. They pried the piece away from the rotor and the brakes work ok now. Have not replaced brake fluid - don’t know if I need to.