We have a group of 3 that one car faults out with Number 7 negative target distance and indeed the car is 1/8 inch below or above the floor. We have learned the shaft, relearned the shaft, replaced the gov. encoder, the motor encoder, checked and replaced the wiring from each encoder back to the controller. We get this intermittent shut down, with no rhyme or reason. Sometimes it will go 60 days with out shutting down, and then it happens every other day.