I had a chance to look at the height sensors and there was nothing visibly wrong, so I gave them a good clean but the problem still persists. I really wish I knew if it was one or both, so there was a possibility I wouldn't need to spend money on a part I may not need, especially with their price. :( This is going to have to wait until next year to be fixed properly. In the meantime I've disconnected the headlight motors.