With the switch pressed in (ie. sled is at center of CD hub), I get no
resistance (00.0 on the multimeter display). But with the switch
released (ie. sled is anywhere *except* right at the center), I get a
reading of 47.8 on the multimeter display. These results are both
using the 200K scale setting on the ohmmeter.

I would have expected infinite resistance, not 47.8, with the switch
released. So that's a bit surprising. The switch isn't perfectly
open when the pin is released, although there's obviously much more
resistance than when the pin is pressed in.

Did you disconnect the switch when you tested it? If not, then you
are reading whatever it is connected to when it is open...

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