Worn bushings on my SDL would sometimes prevent engagement of D, even though the shifter was in the correct location. To compensate until I got the bushings replaced, I would usually shift to "3" then back to "D" to ensure it was in a forward gear. Sometimes that would result in being stuck in "3" instead of "D", but oh well, it was forward.

Replacing the bushings put an end to that misbehavior. Haven't had a wrong shift since.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]