Occassionly my A8 drops on the near side rear corner overnight, but returns to normal as soon as I unlock the car. I have no problems with the suspension in daily use, but I do get the fault code 01772 - Signal from Level Control Pressure Sensor.
Reading around has not led me to a likely reason of why this fault occurs in isolation. I'm about to look for the "massive orange fuse" mentioned in this thread,
http://forum.a8parts.co.uk/showthread.php?t=2864, but is there anything else it could be?