Quoted from cooked71:
But couldn't find anything on hit sensitivity. The crane switch works when the spring touches the metal hole that the spring goes through at the bottom of the end of the crane arm, thereby closing the switch. Given you cant seem to soften the spring tension, the only way I can imagine you can improve the sensitivity is to make the hole smaller, or the spring larger. You could get some conductive tape and wrap it around the spring - not sure this would work but worth a try. You could also somehow make a smaller ring to make the hole smaller - like a cliffy magnet protector.
Yeah its a simple switch design, which is why I think the manual just shows you the schematics of how it goes together, because there isn't a switch as such. When my BDK stopped registering a good % of hits, I used the manual to take it apart and if I remember correctly found the plate that the spring attaches to had shifted slightly, put it all back together and it worked perfectly again. Unfortunately the manual is more of a how to take it apart and put it back together guide rather than here is how you fix it.