I have not tried adjusting the blue plastic shim. Perhaps the window is too cambered to the window seals, which makes a good fit but at the same time results in the retention assembly being pushed away slightly from the L bracket. When I acquired the car, these bolts were loose. I tightened them but did not check the adjustment. I did not know at the time that the blue shim served an adjustment purpose.
The next time I feel like removing the door panel (yet again - how many times have you done this...) I will adjust the shim. Tightening the bolt on the retentions assembly always makes me a bit nervous. I know it is 7nm, but I am always worried of overtightening and breaking the glass (or leaving it too loose and having to open the door panel again at a later point).
If this adjustment does not work, I will just add some washers to the L bracket so that it stands a bit further out.
When I eventually get around to doing this, I will report back. Thanks everyone for your advice!
