This is my old s.2 car, and this problem is a mystery to me too. I don't recall ever having this situation, but then again, maybe didn't have exactly the same conditions? On the other hand, of course the car was up in the air and there was the droop....
Just trying to think this through - with the droop, perhaps additional air or pressure is coming from a bleed of either air or oil from lower part of suspension tower? Not sure what else it could be, and also not sure about this either.
Maybe get rid of the 50W oil, go back to 20W or 30W, and see if the problem replicates?
Sorry not to be more helpful...
Geoff