Fault code 480DB0

Do you have the factory BMW INPA/EDIABAS software and vehicle interface? You will need that to run through the test schedule for the suspension system. Without it you are flying blind on a system that can make you nuts, even when it does work!

The code means the computer thinks it is taking excessive time for the suspension to get to the proper ride height.
I would start at the compressor and work my way back along the lines, a small leak or a bad valve could easily cause this. As could a bad height sensor.

If you have the correct software you can go in and look at the ride height the sensors are showing and reset it. If you change any of the sensors you will need the software to reset the system to match the new parts.

That should work. You should find a section in it that covers the suspension. It should have guided tests that you do to check the system piece by piece. On of those should be ride height. It reads the height the computer thinks the car is at and shows what it is set at. So if you go in there and it is showing a ride height of say six inches and the sensor is showing six inches but the car is on the bump stops you can tell the sensor is bad.