Turn Signal Sometimes Won't Cancel

[mbsickness]

I have an '02 ML500 and sometimes (once a day) when I make a right hand turn where I unwind the steering wheel slowly....the turn signal won't cancel. I do know that this is relate to a physical component vs an electrical issue. Does anyone have an exploded diagram of the steering column including the turn signal? My car's about to fall out of warranty and since tis doesn't happen everytime...the dealer is not doing anything but saying "cannot duplicate problem" Thanks in advance.