I was parked on my driveway after washing my new-to-me '07 RRS earlier, went to adjust the ride height from 'off-road' back down to access, when it complained that there was an obstruction and raised the car up all the way.

After driving forwards and back, it let me adjust the height as normal, but the rear left arch gap is about 15-20mm more than the other corners, and the white block is showing as slightly higher on the display (in access mode the display shows the other three white blocks touching the top of the wheels, but a gap on the rear left).

Any ideas what causes the detection of grounding and if its a calibration issue or if it needs replacement?

I took this in to my local independant who plugged it into the computer, no faults showing and everything acting normal. They said this can happen if the car has been used at road height most of the time and is then used off-road for a bit, because the height sensors corrode at the higher settings, then give spurious readouts.

Most likely caused by a poor calibration, or blocked compressor dryer

Thanks DM, is the compressor drier user serviceable (checkable?) or should I take it back to the garage...