I assume it turns ok for you to get it to the tilt so the winder cant be stuck. The problem I think is with the way it carries out the next stage. My front unit was exactly the same when I got it. Fortunately it did go to the next stage with a bit of a clunk until I found that the screws were loose and the glass had moved well out of position. (if for example the glass is too far forward it cannot tilt far enough for the mechanism to get into the right position) If you can get it to tilt up fully you might be able to reposition the glass using small torque spanners (like allan keys) or remove it completely and get into the mechanism. If you study the rear unit you'll see how the slots work the mechanism. try using a thin screwdriver to nurse the pin in the slot and if that doesn't work consider using a small mirror to check the tracks aren't jammed with a small stone etc. Good luck