Hi,
I have a GLC Coupe and the rear window has stopped going up and down despite the motor still working. When I removed the door panel it looks like the window is not sitting on the runner. I tried to put the glass back onto the runner but when I tested the window the runner moves however the glass doesn't. Nothing seems to be missing/broken on the runner however the glass just seems to sit on a a small piece of rubber on top of the runner is this correct?

Any advice is appreciated.
Thanks