Well, looks like it was the easy fix. The knob shaft was cracked. I
super-glued it, then wrapped it with safety wire and coated it with JB Weld.

My wife was laughing, because I told her I could get a new one for less than
$10, but I wanted to try and fix this one :-)

BTW, if the panel with the control unit has to come out, that whole bezel
that also houses the Speedo and Tach has to come out as it looks like one
solid unit.

Luckily I don't have to do that!