That's what I think when I remember how stumped I am. Maybe you guys know. All disk brake with abs. New pads. Completely clean and greased caliper pins. Booster holds vacuum. Did the pump test. Heres the issue. Intermittent hard brake pedal BUT with plenty if not 100% brake assist. While the hard brake pedal feel is occurring, the brakes drag sligthly .Goes away on its own while driving. Comes and goes. MC is 1 year old. What could cause this? A temporary fix is shutting the car off and pump the brake pedal till its rock hard. Then pedal is 100% normal.