Could be a ghost switch means that a wire is soldered to the wrong side of the diode .
Check first the standup targets .
The white wire has to be at the opposite side of the band of the diode .

The two symptoms you are seeing are actually kind of contradictory. If I had to guess I'd say you've got a little mis-wiring going on. First thing I would do is go into switch edge test and go through and test all the switches. Make sure the correct switch indicates closed and make sure closing one switch doesn't cause two to show closed.

Switch 42 is on the trough under the playfield. It must not be working.

If the ball makes it to the slot kickout (switch 52) without triggering any other switches, the game assumes it was shot into the slot machine.

That helps make sense of the symptoms, and as you said would indicate switch 42 is not working.

Sorry to dig up a coffin. Does anyone know the part number for that switch?

The manual says switch 42 (Mini-playfield Top Hole) is part 5647-12693-13, which is available at Marco. That's a pretty standard microswitch.

What switch are we talking about again?

The Camera switch. I thought it was one under the playfield? The insert decal labeled "THE CAMERA" points under the miniplayfield. For some reason, my switch doesn't work ("Check switch 42 THE CAMERA" on test report). Is it the same 5647-12693-13 switch?

It's under the playfield. It's one of many switches on the trough. You probably just need an adjustment or have a broken wire or something, but you should be able to verify from the manual that that switch is the one I mentioned.