The bearings in the metal strap that connects the door to the chasis post have jammed... probably due to rust or wear. To check out the assembly you have to remove the door panel. Small 10mm bolts hold the strap assembly to the inside of door hollow. If the strap assembly is salvageable ... try greasing the bearing that slides along the track. If not, a new assembly can be purchased readily from parts shop.
1993 190E 2.3
2000 Toyota 4x4 Tundra