On O22 switches, adding to the repair information.
A problem that I've seen with many of these switches is a malfunction of the non-derailing feature on the curved route. The cause is an short or open circuit on the insulated piece of curved rail. The symptom of a short is a switch that insists on jumping back to the diverging route when you throw it to straight, with a chatter if you hold the control lever. If the non-derailing doesn't work on the curve, it's an open circuit at the same spot.
Here's how to fix either condition.
Take the bottom plate off by removing the there screws marked with a white tab in the first photo. On later models there will be slotted round head screws. Removing them takes socket wrench or a very tight frip with the right kind of pliers.
The next photo shows the connections on the bottom. Note the arrow on the left pointing to the non-derailing curved section. The double arrows on the right shows the two pins that connect the detector rail sections to the motor. Those touch the four contacts that FRV recommends polishing.
The problem is with that blob of solder that connects to the non-derailing track section. Looking at the photos, you can see how close together are the clips that hold the two curved track sections to the base. If the solder touches that other contact, the motor coil throwing the switch to the curved route will be constantly energized and it will return automatically when you use the controller to switch it to the straight route. You can break the connection with a soldering iron. I use insulating tape to ensure the problem won't recur. Then you need to re-solder the connection while using insulation to make sure you don't cause the shorting condition - difficult but can be done.
The shorting condition will also occur if that solder blob contacts the base plate - the main reason for that insulating card.
