the pistons in the calipers are getting egg shaped as they come out of the caliper and do not retract properly.
Go to a Nappa store for a rebuild kit. They sell the best and most ford vcm 2 reliable parts for this kind of repair. I just cant remember what the outfit is but I think its Bendix,,but its a USA outfit.
Thats the simple answer. The worst case scenarion is the brake line system has been F------p from day one and the dealers were idiots.