Well after cleaning up the pin contacts a bit and swearing how the car will end up in the crusher, outloud so that the car could hear it
In any event the switch seems to work fine now, repeatedly, let's see how long that holds out.
Thanks to duxthe1 and the others for some great suggestions. I think this came down to two causes. The fore/aft being the most often used seat eventually bends the contact arms to the point where a weak contact is achieved. After correcting that problem, and still having erratic operational issues, weak/cracked/cold solder joints as duxthe1 suggested were rectified and now all seems well.
The later switch design is far simpler mechanically to service and rectify over the earlier design with all of the springs and ball bearings. It has no pieces that fall out of place or need to be tracked when the cover comes off and it is a very robust design, but like anything in use for 20+ years, some corrective adjustment is acceptable and expected.
I also picked-up a spare from the junk yard and unfortunately that also had a few non-functioning switches, so I'll tear into that one and post the findings here. My main curiosity is how to separate/remove the board fro the plastic housing, if one wanted to replace an individual switch rather than repair it, how it could be done. Also of interest is the shared electrical pathways on the circuit board that go between switches. I'll try to take some detailed pictures of the board layout front and rear.
Thanks to all