I disagree. Toe-in changes any time the car's height changes, and that is common as the front springs sag.

I assume you sprayed WD-40 on the stuck threads and gave it a day to sink in. Try grabbing the fat housing of the tie-rod end with a pipe wrench or large vise grips. You could also try heating the threaded end w/ a propane torch until red. Worst-case if you force it is you would need a new outer tie rod end and adjuster. You can buy those for most U.S. cars, but perhaps junkyard for M-B. Mine were never stuck, but CA cars and don't know if you live in the salty north.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans