Shift link bushing...
The shift gate stops the lever from moving the NSS all the way into contact position b/c of bushing wear..[ can't get full throw from linkage]

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=21H0MN3YU24P0SESWY&year=1988&make=MB&model=420-SEL-001&category=J&part=Shift+Lever+Bushing