Here is a switch off of a Lasonic TRC-920, I'm not 100% sure, maybe 92.3256% sure these are the same switches used on the 931.
They seem to have a small gear inside that either slips off the knob shaft (he he, knob shaft
) or the gear breaks.
I think these could be repaired or maybe someone needs to have some gears 3D printed (I'm looking at you Miles)
The sucky part is you have to unsolder it from the main board to work on it.
#TerribleDesign