I recently acquired a 9530 Joel Chandler Harris passenger car, and both of the long coupler arms were drooping down so badly that the couplers wouldn't connect with any of the other passenger cars of this series. The tang of the coupler pivots from an outward projecting tab on the top of the truck saddle. This tab has a hub which mates with a hole in tang. The tang is held into place with a black plastic piece that sort of resembles a dearth vader helmet. So the tang is sandwiched between the tab and the dearth vader helmet. See the picture below. For some reason, the dearth vader helmet wouldn't hold tight, causing the coupler arms to droop downward. To fix this, I wrapped the sandwich with a 4" black plastic zip tie and cinched it real tight. This seems to have solved the problem - the coupler no longer droops down, it lines up with the other cars of this series, and the coupler arm pivots freely.
Here is a picture that shows the coupler arm after the zip tie was applied. The arm stands straight out without any drooping. I did this on both ends of the car.