You don't need solder.Lucky my 2 and 3 just doesn't work and 4 flickers. I have to turn it off and on off and on for it to stop flickering.
I have yet to do this because I've had other issues and no solder.
Take the switch out, take it apart and clean the copper contacts inside the switch. it will work like new. See my post above, i did this several months ago and it still works perfect.