thank ECS for the wonderful pics.

Ok so take a look at this link

Home Page > Search > 51338254781 > ES#94509 Window Regulator Clip - Priced Each - 51338254781

Look at the 3rd pic. The nut goes inside that sleeve / collar.

You should replace that plastic clip thing. When you clip it into your window, you then insert the nut from the outward side in. When you tighten the screw, it pulls the nut inside the collar, expanding that collar, and holding your window in place.

Let me know if you follow.