After 6 months ours started displaying the 4WD warning too. It is never on just after start-up but will display anytime within the first minute. Usually if it doesn't come on within a minute it won't come on at all.
So I bled and replaced with Matic D in the Attesa system and replaced oils in transfer case and both diffs. Problem remained.
Sometimes I can sense that the warning light is about to display. When driving away the car will bind up slightly and want to straighten up - like as if the centre diff is locked and the fronts what to rotate at the same speed as the rears. The warning light will come on, the steering will relax, and I guess it then is a rear-drive only?
Also, if the car has been allowed to fully cool then the warning light won't display but is very likely if the car was recently switched off.
My next attempt will involve reading those fault codes.
