If leaving my car 2-3 days the rear back suspension loose pressure. The 4x4 screen show clearly that this sensor is indicating. If leaving the car a week it "sits on the wheels".
I have also noticed, not sure if is related, that the light come on on the dashboard indicating suspension fault. This happens randomly, light is first yellow but sometimes turn red. If I stop and turn off and on again the indication is gone.
Any clues?

Plenty of clues there,you have a leak.Your light will be coming on because the system will be failing to reach pressure in the set time,so it shuts down to save the pump.

Thanks for the information. Any idea where I shall start to look?

My first place would be the connections at the dryer on the compressor,very easy to do just remove the bottom cover and you will see an orange and a blue fitting(high and low pressure)spray with some soapy water and I'll bet you see bubbles.The heat that is created in there distorts the plastic pipe.I've just replaced my compressor because of this for a new style one and the pipes come with a metal insert now hopefully to prevent this problem.Then if it's not there its just a case of working through the system,air tank,pipe connections on air bags etc.
Good luck
Steve

Many thanks. This is extremely helpful. The fact that rear back sensor indicates first, both on the display panel and physically, it is visible that the right rear back is slightly lower than the other three wheels, does this possibly indicate that the leak is on this suspension?