This surprises me as the perspex bit of the window is held in place between rubber seals and would have to be prized out. Are you certain someone has not tried to break into the van by removing the window?
i had a lunar freelander and the same thing happened to that, but on contacting the company it turns out it was a dodgy batch of doors, and my van had slipped through the net due to the previous owners not registering the van or something like that, a fitter came out from the company and changed the full door free of charge
------------- If its not broke, dont fix it, and stop nagging
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