The spinner's plunger and switch had to be the culprit of the "lousy design". To test that theory, I eliminated them by clipping alligator leads to the switch's two solder tabs and then machine-gunned the hell out of wire ends. That confirmed it.
There are actually two mechanical issues that really do show poor design, both of which needed to be addressed:
1. the factory plunger only applies force to the switch blade in one direction: down. The plunger' shaft also interferes with switch movement as it scrapes against the leaf's hole edges. Whenever I tried to adjust the moving switch leaf for greater upward force, it caused the spinner to lay flat and not work. There was no happy medium. So I removed the old wire & weight and formed a new plunger with loops at both ends, one of which hooks permanently into the hole at the end the switch leaf. (I know some Bally designs do it this way, which is probably why they work so well.) That allowed me to bend the switch leaf as far as needed to balance much stronger up and down forces that offered a wider contact gap. I removed the entire assembly to do this. The picture shows the side by side comparison of the plungers (factory on right).
2. the switch blade contacts need to be gapped at least 1/8" - 3/16" apart. The plunger makes such deep sweeps up and down that a normal gap will not allow enough clearance and dwell time, particularly at high speed cycles.
If someone is not happy with the scoring of their Gottlieb spinner, this is a solution. It takes patience to adjust the tension and get it right. But it works.SC new spinner pushrod (resized).JPG