I had a similar problem with my Plus 4 with centre lock wheels. The first pair of discs were replaced under warranty due to warping. The new ones were okay for a while and then went the same way. I then found a garage in Langport in Somerset who skimmed the discs on the car. All has been fine since with no indication of warped discs i.e. no pulsing of the brake pedal. I’ve no idea what the cause of the warping is but the skimming fixed it.
Bob.
