Dis assembly is a bit trickey. When finnaly pulled apart, I found that the Outer knob has a COG that rotates the shaft of the rorary switch with a smaller COG. The large COG was split with not much face to re glue.I decided to try to make a replica using Fusion 360. After many hours of design and printing 3d drafts I got a cog that works. A bit rough but fits on the shaft and works, all 24 teeth mesh OK and the knob feels normal.
Now I will try to make replacement FIP knobs.
