Quoted from NPO:
You're welcome . Glad I could help. BSD is quite a unique beast, and yeah, if you're getting that error, that means that switch more than likely needs to be adjusted. If I recall correctly, you can tweak the metal arms that cause the switch to "click" when it is engaged.
Typically, when you "occasionally" get a switch error, that means that switch is not being tripped for x > 30 games or so. So what's happening for you is most of the time the switch is not tripping and then randomly the ball rolling over it gives just enough force to engage the switch and the switch error goes away.
Take your PF glass off, bring your table up and out, and identify which switch is 41. I am pretty sure it is the 4th switch or the first one the ball rolls over once exiting the PF. Trip it with your finger and see if you hear it "click" - basically your hand is acting as the ball. If you do not hear a very obvious "click", try adjusting the metal arm. Test your other switches so you know what to expect from the "suspect" one. Always do this kind of stuff with the game off and unplugged from the wall. You never know what can happen with the game on or plugged it - trust me on this one.
If you clearly hear the suspected switch "click", fire the game up, go into switch test mode, and re-do your tests on the suspect switch. If the suspect switch activates in switch test mode, start a game and enable the coffin or castle multiball, then play the multiball out and see if when all but one ball drain that the mode stops. If it does, you're good my man!
Let us know what you find !
I finally got around to solving this issue! I had two issues going on actually. The switch 41 error was coming up (switch in ball trough closest to the shooter lane). It was actually not the switch but the wire that sticks up into the ball trough was binding and not working correctly. So I readjusted that and all is good! The second problem was the ball popper arm that pops it up into the shooter lane was not returning down like it should. It was VERY slow. So basically it would stage a ball in the shooter lane then stick up and hold the remaining balls in the trough back confusing the machine. So that combined with a bad switch 41 the game was going crazy looking for balls, auto launching balls, never ending coffin/castle mutiball, error codes, just weird stuff all around. So if anyone has issues like this, the solution is most likely the machine losing track of the balls. All is playing 100% now!! Thanks everyone for the help,tips and insight. The knowledge of these machines on this site is truly awesome!
Edit: I forgot to tell the solution to the slow popper arm. All I did was clean the linkage and a drop or two of PB Blaster on the arm linkage. NOT the coil itself that would be bad haha. Anyway it's perfect now.