several things could affect ball travel
are machines level?
pitch of machine?
cleaned and waxed?
raised/cupped inserts (although the two titles you mentioned shouldnt have this issue)
bubbled mylar (although the two titles you mentioned shouldnt have this issue)
some Sterns you want to nudge the machine when the ball is leaving the orbit to return it back to the flipper, MET is one of them (if your talking about how the ball returns to the flippers)