Date registered: Dec 2005
Vehicle: 222.132 & 221.122 & 213.050 & 906.633
Mentioned: 3 Post(s)
Quoted: 40 Post(s)
I guess this has air suspension based rear level control. You don't have any malfunction indications? There is only one level sensor, that should not be the issue then.
If the air bellows was leaking, the compressor should be running a lot and you should notice that.
Cannot think about anything without seeing it, perhaps you could post photos.