Try a different dealer. It doesn’t stand to reason that if they will replace a part 2x due to it being notchy and then refuse to do it a 3rd time. BTW, my ML had the same problem and the dealer replaced the pedal and the subsystem that goes with it. Another solution is to find out what is used to lube the mechanism and where and do that.

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...Tracy

'00 ML320 "Casper"
'92 400E "Stella"