Symptom typical of bad height sensor. These are user verifiable with a multimeter. Somewhere on here I put the pin codes and related. In a nutshell you have 3 lines for the air suspension. Ground, 5v source, and a variable voltage based on position. Runs between about 1, and about 4, volts.

Some height sensors also have outputs to the LCM for the HID aiming, so be cognizant of that of you have 6 wires vs 3 at a given connector.

You can disconnect the arm on the height sensor and back probe the wires easily.

If you have INPA it's easier since it tell you real time what the height sensor is reporting.

Typical fault is when the voltage for the height stays low and unchanging. Car tries to raise but voltage doesn't increase as expected. You get a fault.

Common reason for this is the shaft seal on the height sensor wears over the years, and water intrusion can occur. Then corrosion, then failure.

If you don't have a way to diagnose, and your symptom is suspension inactive and one wheel jacked up out of kilter from the rest, start with the easy to check item - height sensor on that corner.

If you have INPA, you can manually put the heights where you want them, then set it to ignore plausibility checks (or something like that; I forget exact terminology). This will keep the car at the height you set (assuming no leaks and stuff; it won't self-correct in this mode). That way you can drive around as usual every day until part shows up and you feel like changing it out. Then put it back into normal operation and clear fault. All happy.

By the way, this mode is the easiest way to experiment with different ride heights and stuff, too, since it's essentially full manual control.