Air suspension and height control is only on rear wheels in Prado 120. So, your front suspension might be old and need replacing. My Prado's air balloons on rear suspension leaked after I took it to off-road track on Deosai Plains. Replaced the balloons and it was good as new. But after few years the front suspension started getting uncomfortable, I would feel small bumps on road, but big bumps were comfortable, weird. Later I sold it to a dealer and he pointed out that front suspension needs some work.