Not always, but often enough, I get run on scoring associated with the drop targets on my SS Mata Hari. I might hit a target and hear twice the number of chimes as normal. Alternately, the ball could be in play elsewhere on the playfield and chimes and points rack up as if a target or targets just dropped. I thought for sure it was a bad diode on one or more of the drop target switches. I just desoldered a leg free on all eight diodes and checked each one out of circuit. Much to my surprise, they all check good.
I've started trying to isolate switches by inserting a sheet of paper between the leafs. With all but the lower right switch blocked I get the following behavior. If I drop the one active target, it scores normally. If I drop the disabled target next to it, it also chimes and scores. The same is true if I drop the upper right target in the same bank. What does this tell me, and how should I proceed?