The title is Strikes & Spares, and the row of switches is row I5, which includes a bumper and a few other switches. When the game is powered up and into game play, if any of these switches except for the bumper is actuated, everything is fine. However, when the bumper is actuated, not only does the bumper not work, but all the other switches in the row no longer work, and won't work again until the game is powered down & up again.
So I figure that there is something wrong with the bumper. The diode checks out, and as I don't have a multimeter capable of measuring the .047 μF capacitor (one is on the way!), I just presumed that was the problem, so I put another capacitor in parallel to the one then installed, and the problem disappeared ... for a little while; now I have the same problem, as I am currently down to only 1 good .047 μF capacitor (more are on the way!), I don't want to sacrifice it until I have some explanation.