My turn signal/multifunction switch does not lock down when activated. I've read threads here about a simple fix that involves filing a new notch that allows it to lock in place. One of those threads had pictures, but they don't show up anymore. I've had the switch out of the column a few times, but can't figure out exactly where to file these notches, even after studying the operation of the switch. It seems really smooth, like it was never meant to lock down in the first place. Can anyone advise me? I've attached a few pictures.

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1976 240D "Katja"