Hi. I have a 2006 400H from new which up to recently has run beautifully. The problem now is sometimes It feels as if my brakes engage slightly mostly on long journeys causing the car to not run smoothly for maybe 5 mins and then seems to release and run smoothly again. The mechanic couldn't identify the problem and it was identified in an NCT (MOT). The back brakes were replaced with calipers which solved the problem initially but has now come back. Any thoughts .