Try the shifter bushings first. If you aren't able to push the linkage all the way into "P" it seems plausible that it may not engage the parking pawl. Certainly worth the $5 in parts to fix and see if it fixes the parking issue at the same time.

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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]