InterestingI had a similar issue with my old bike. I thought it was a warped rotor but it wound up being user error. I was a noob and when I came to a stop I held the front and rear brakes until I was ready to go. The front disks get hot and cook pad material onto the front rotor. Every time you stop the discs tend to stop at that same spot due to the extra friction. It also causes a pulse every time the pads go over theat spot. I changed the pads and cleaned the rotors then started using only the rear brake once stopped. Never happened again.