I can't tell you how to get it out. Put I can tell you that likely your window regulator has stripped some teeth. The exact same thing happened to the passenger front windows of my '84 300CD.

My rear window surges and its on the list to look at. Perhaps I'll try and take it apart tonight and see if I can figure out how to get it out.

There should be a couple of bolts that you can see on the body of the car that you'll have to remove. As well as a few bolts that hold the regulator to the window glass.

For the front window I had to remove all these bolts then pull the window up and hold it out of the way while I wrestled the regulator out of the door.

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'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.