As I said I'm not an auto park expert.
But I know a bit about the service brakes.. On my W series they are HYDROBOOST
This means they use power steering pressure to boost the brake pressure....
I'm wondering where the Auto Park gets the pressure to release.. Can it be from the same source.. IF SO then if it is leaking the result would be a loss of Power Steering/Brake fluid and.. Well. this could cause problems.
HOWEVER I DO NOT THINK excessive brake pedal travel would be one.. When pressure is lost it is HARD braking (Hard to press) YOu can tell this because with the engine off if you press the brakes the electric pump that kicks in is not as fast as the engine powered pump so the pedal goes down... SLOWLY .