Is it possible that diverter is not the original part and a previous owner "made it work?" Or more likely, the factory ran out of the required diverter and "made the other one work."

Did you purposefully use the smallest font available? Some of us folks are getting old.
Just ribbing you man.

Hopefully someone else here has one to look at. You could try PMing some of the other owners on the site. Type Pinball Magic in the archive and click on the owners tab. Then select another owner and send him a message. Fatsquach is probably your best bet as he is pretty knowledgeable.

You should update your "Collection" in your pinside page.

Well, hopefully other owners will know how to answer the diverter question.

Old SS pins are good too. I have a couple. There's no such thing as a bad pin collection (unless they are poorly maintained.)

What is the problem with the stage up and down switches?

Gonna look at the manual for you but my guess the switches are optos which are little Infra red LEDs on a tiny circuit board.

Look on page 82 and 83. The optos are shown as a * on the diagram and as part number 4 on the list. There are four of them.

OK, then those aren't the optos.

Could be the switch is inside the motor itself. If the motor is "stepped" it will know when it is in the up, down or in-between position. Not sure how to test for this though and it is just a guess since I've never played a PM. Sorry.

Switches 58 and 59 connect to the switch board at Connector J6 pins 3 (Blue/Red) and 4 (Blue/Orange). Look at the colors of the wires at the pins and backtrack these wires to the switches. IF these wires go into the motor, then I don't know if the switches can be fixed without installing a new motor.

Yeah, thats the problem with these games with a lot of mechanisms. Can't easily get to any of it. It's like trying to work on small cars with the big engines.

My pleasure. I love puzzles. And wiring diagrams are a huge puzzle.
Glad you got it worked out.