I believe this to be a deliberate design so that the part fails and needs to be replaced. 3 windows have gone on my 4+ yrs old car. specifically it is the green or white plastic clip that grips the window. if you google "renault regulator clip" and click on the image results u will see they all break in similar ways. My local Renault garage quoted me almost 300 euro to fix. I purchased the part for 30 euro and fixed myself. it took time and hassle, but for the sake of it, i did it myself. now it has happened again to another window, the part is now 12 euro, but is out of stock, so the car has a SERIOUS security weakness now ( the window just falls down and cannot be locked). The replacement part is more robust than the original. I find it very hard to believe that this is accidental, or an oversight, i think that it is a deliberate ploy to get you back into the garage and help generate business for them. The only alternate view is that Renault did not test it, or do not care that it won't last beyond the standard 24 month guarantee.
i feel totally cheated by a piece of cheap plastic and some very questionable design.