I think that you are getting too much declaration too soon in the Pattern. This causes the car to hunt (come in too slowly) at the floor. If a leveling switch is open or shorted, then you get a slower step of slowdown too early and the car rapidly decelerates. Also, you could have a slowdown resistor open at the final steps and that would open the gen shunt field circuit until another slowdown jumps it (the break in the resistor) out.
