E280 sport estate w211 rear suspension

[Andy Rim e280]

My e280 sport estate is slightly lower on the offside rear by about a half inch. It doesn't get any lower but also it doesn't rise as it used to to level it with the near side. My thinking is that it it could be a level sensor as if it was a leak it would just keep going down until it bottomed out. The car is not airmatic just self levelling on the rear. No warnings seen on dash. Any ideas?