I currently have the SUV in the dealership because the rear air ride suspension keeps dropping about 2 1/2 inches after the car sits for about 3 hours. The suspension drops evenly on both sides. Initially the service dept told me I needed to replace the air bags and the compressor, but the leak still occurs at the same rate after the items were replaced. They have checked for errors in the computer system, but nothing comes up. They tried re-setting the system, but that didn't work either. Now I am being told that a certain amount of droppage is expected, but I have had the car for 6 years and this is the first time this has happened.

Any ideas on what this might be?