Kerry The tumblers in side are worn . You need to remove the barrel, and with the key inside the barrel , look, and any tumbler that is sticking up is the one thats the problem .I just file it down to the same height as the others pop it back in after you put a little oil on to the tumblers.. Just did mine but i have a W124 i think the removal of the tumbler is the same. I will check for you . #