This may have been covered before, but I noticed today that the crossover/upper flipper ramp shot on mine had the right wall sitting slightly in front of the lane guide leading to it. Basically, the guide was leading the ball to smack the edge of the ramp wall, definitely contributing to rejects. Pick is after adjustment, should have taken a before but didn't think to.
So, I managed to move the lane guide in a bit to line it up with the ramp. Filled the screw hole closest to the wall with toothpicks, didn't have to drill a new hole but I think that gave it enough support to screw it in a bit farther forward and hold the wall in place. Loosened the ramp to shift it a bit too, but not much play there either, so probably not relevant.
At any rate, something worth looking at if you're having issues with ramp rejects. Mine was knocking back shots quite often.