Hello. on my 2012 S550 (W221), the driver and passenger side suspensions are behaving differently from each other, and I am not sure which side is behaving normally/as-expected, and which side likely has a fault. I am a new owner and requesting help from experienced owners/technical-experts to determine which side has fault. The car has 137K KM on it.

SYMPTOMS: When the car is turned off, and is parked, the driver side body, both front and rear, stays raised at the same level as it was when the car was started/driving (that is: the gap in wheel wells between the body and tires remains a few inches). However, On the passenger side, both front and rear, the body goes down when the car is turned off (that is: the gap between the body and tires is completely gone), and rises when the car is started. Furthermore, even when the car is started, the gap between body and tires is still more on driver side (the side that never goes down) than the gap between body and tires on passenger side (the side that goes down when car is shut off). If I bring my ears really close to passenger side front suspension (the side that goes down when car is turned off), I can hear a hissing noise when the car's body is going down when car is shut off.

I am not sure which of these two sides are showing an expected/normal behaviour. If the car's suspension is supposed to go down when shut off and rise when started, then passenger side is likely working OK and driver side has fault. And vice versa.

MORE INFORMATION: When the car is driven, the ride comfort is greatly compromised (hard suspension), and there are thud noises when car goes over a bump or a break in the road. The only messages we have seen on dashboard are following. only once, when the car was started, it said "car rising" or something like that. And then, only once, it said "malfunction". No other messages or dahsboard lights have ever come up. We have been experiencing this issue for over a week now, and have driven a total of about 75-100KM with this condition.

Please help me determine which side (driver or passenger) needs attention. Also, what is your best guess as to what might be wrong? I will take it to a mechanic for repairs anyways, but I want to be well informed about this hence the request for help here.

Thank you!

PS. I wasn't sure of the best place to post this question so I am posting in both this forum, and W221 forum. Sorry if you are seeing it twice.