My 1992 300D 2.5 is wired for the rear fog lamp, and it works. The problem is, 9 out of 10 times when I pull the knob out to the second detent, it just comes all the way off. I've inspected both the knob and the switch, and I can't find anything that is obviously broken - is there a plastic tab or something that is supposed to prevent the knob from coming all the way off?

Also, what's up with the orange dot at the center of the knob? Is it supposed to illuminate or something?

TIA.