Quoted from interrobang:on some ball drains where the ball will drain to the trough but the game will just sit there without paying the bonus or launching a new ball
If the bonus doesn't score when the ball drains, Inspect and diagnose this circuit with Alligator clip jumper wires
http://www.planetimming.com/Pinball/troubleshooting/EM%20Troubleshooting.pdf
http://www.pinrepair.com/em/index3.htm#features
For a switch to work 3 things are necessary
1) When open, there should be a small space between the contact points (duh)
2) When closing, the long blade's contact point should push the short blade's contact point enough to move the short blade
3) The contact points should be clean, which they usually will be if #2 is happening