Hi Matt,
Are you operating the trolley at low or high speed? If the speed is set too high, the trolley may have too much momentum and overshoot the sensor, and trip it again when it reverses.
There is a slight buffer after the sensor is tripped to allow the train to get moving. Reducing the speed will allow the trolley to stop and reverse quickly enough that it should be able to get away from the sensor in time.
Are you operating the trolley at low or high speed? If the speed is set too high, the trolley may have too much momentum and overshoot the sensor, and trip it again when it reverses.
There is a slight buffer after the sensor is tripped to allow the train to get moving. Reducing the speed will allow the trolley to stop and reverse quickly enough that it should be able to get away from the sensor in time.