got some advice a while back which i'll pass on to you. whenever you have any brake related issues always do a fluid replacement and bleed. suction the old fuel from the reservoir get all the soot out then replace with new fluid. then do a bleed. 9-10 be it sticking calipers, or abs issues this will help. You would be surprised how much soot is in the reservoir. This should actually be routine maintenance every 30k miles.