Don't know the setup on a 123, but I can tell you that removing the front door handles on my 124 took more effort than removing the back handles, even though the written instructions were the same for front and rear. On the 124, there's a 3mm hex head screw under the weatherstripping lining the door, and that screw holds the handle in place. Apparently, the 123 uses 3 screws of some sort to do the same thing. The instructions say to turn the hex screw 4 turns and that will be sufficient to loosen the tension on the handle and allow it slide back and out of the door. Not even close! After 6-7 turns, it was finally loose enough that i could jiggle and wriggle and cajole it out. I suppose the key lock mechanism has something to do with why the fronts were so much more temperamental than the backs. Maybe you just haven't cajoled 'em enough?

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't