I have an S120FT-PRS that has an issue with the control valve. It has a 5 function electronic valve with mini-lever switches on the armrest. When operating other functions i.e., tilt, or clamp rotate, the carriage moves upward. And sometimes without operating any functions you can see the lift carriage slowly creeping higher. I have tried replacing the mini-lever switch and the control module beneath it, same results. Any ideas?