The standard answer on Xantias, BXs and the like was the rear height sensor.
There was a plastic clip which connects the suspension to a valve which
controls the rear height. The plastic clip can break or the valve can stick.
Unfortunately I've given away my Xantia Haynes BoL and never had this
trouble on any of my Cits so I can't help much more.
I'll cross post this to alt.autos.citroen.
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