All three of my 124s show this. As an experiment I bought some rubber coating for tool handles and painted one set with that (bright red!) It is holding up well. On another, I scraped the old coating off, not hard to do, and simply put foam insulation on the mating surfaces -- also serving the purpose and holding up OK. On the five speed euro, number 3, I have yet to get to this small of a detail yet

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W108M117(1972) repaired after deer hit
W124M103(1987)
W124M103(1989) -- sold to son's friend
W124M119(1993) --
W124M103(1987 -- 5 speed Euro) - sold to forum member
W124M103(1989) -- TE
W123OM616(1977)
W201M103(1990) parts car