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.