Just been looking at these on a van and it seems like the smaller glass panel that slides moves within it's space when you close the sliding door (Ie. it sits nice and evenly initially with a few mm around each edge when you open the door, then when you shut the door you can hear it slightly move (not a pleasant sound), and visually see it's much closer to the front than back - I was not slamming the door either.
Has anyone else found this, or am I being too fussy?