I had the same problem with my 190D project car. The shaft moved and slipped off the hole on one side. It can be pushed back in but it is not a permanent fix. I screwed a piece of flex metal strip on the other side to stop the shaft from moving sideway. I put a dash of grease on the metal such that the shaft will rotate smoothly. It has to be a very small screw and it will fit between a crack near the shaft. I also put some JB weld down to stop the metel strip from moving up/down. I did not take any picture unfortunately. It has been working great.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.