I've had a brake balance a couple of years ago on the track that I never had before. In the end it turned out there was play in the wheel bearing, which caused the discs to push the pads and brake piston back too far. When braking the other side braked normal, but on the side with the problem it first needed to push the piston back out. If I would have pushed the pedal a few times the brakes would have been normal. Perhaps you also have a bearing with some play?