Apparently there is some confusion in diagnostics regarding switch 61. From an old post on RGP:

'Got it figured out. I took the opto board under the Deadworld and cleaned
both optos with a Q-tip and it works fine. Just a little speck of dirt on
the opto to cause grief for the last hour of my life. No biggie. It shows
up as switch 61 in the switch test mode but during the planet test it shows
it as switch 62. There must have been some more last minute changes in
production at Williams because I also noticed in the manual that the switch
32 is not used but in fact it is being used for the ramp entrance. Ok, back
to playing now.

And to help further clarify...

'At the bottom of the planet shaft, just above the gearbox, there is a
board with two optos on it. The optos read a ring with two slots; the
slots are arranged so that the optos read them one just after the
other. The system tries to position the planet precisely using these.
If one is bad, it still works - but the ball stop location may be less
inaccurate.

You either have a bad opto, or a bad joint, or just dirt. You can just
about work the board out without stripping the mechanism, or even
loosening the opto ring. i pulled the housing off of one of mine, made
it much easier to put it back and it is dark enough and the slit small
enough the you can live without it.'