Quoted from Tonup69:These all sound awful - but i guess I can start with the metal file. Trying not to take the stack out, if i can help it.
Rather than dismantling the stack, you can put a meter ( machine disconnect from the power outlet) on one end of the suspect switch blade to the contact to bridge it and see if you have continuity. Obviously, the other side of the switch needs to be open or you will likely get a false reading.