So you also greased the wedge mechanism which actuates the rear vent position? This is easier to do from the cabin side. Did you use BMW special grease for these?

On the seals you could use BMW fluorinated lubricants Carbaflo or newer Krytox.

__________________
E39 530dA -02 M-Sport Messing metallic
E53 X5 3.0dA -06 Sport Stratus grey
E70 X5 40d -12 M-Sport Space grey