If it can shoot insanity falls, the whirlpool should be easy, so that would rule out a flipper problem. Instead, look at the ramp. I'd suggest taking off the rear boulders (two screws) and make the shot and watch the ball. There is a pair of wires that run over the entrance flap; they may be low and slowing the ball. If the ball goes in hard and comes back, see if it is going airborne and hitting the bracket for the switch. If so, loosen the ramp flap screws. Is the clear plastic in place over the ramp (with three screws)? Are the spacers there and correct size?