OK, may be onto something:
1. Decided to remove and inspect the two IDCs on the Stepper Motor PCB (the 6-wire 0.156 & the 4-wire 0.10). Found no cracked solder joints on the header pins, so just reinserted all 10 wires with pushers for now.
RESULT: no change.
2. Decided to follow the 6 wires back from first the 0.156 back to the backbox boards & reinsert the wires; retest--and then follow the 4 wires back from the 0.10 and do the same if need be.
RESULT: Probable temporary fix confirmed by manual Spider Hole test--observed the following:
As previously mentioned, the symptom would occur approximately 50% of the time--or within a handful of spins.
With the manual test, I'd drop the ball in the popper and just let the wheel spin by itself the maximum number of times/duration.
Each time the wheel would spin for 8 revolutions and light a new position on the wheel--so on the first sequence, all 16 positions were lit one by one until the game had lit the entire Spider Web on its own.
(Noteworthy it didn't duplicate a single one--each time the wheel made 8 revolutions, and each time, it landed on a new symbol until it started Spider Multi Ball.)
Turned the game off and tried again: this time the wheel flaked out about half way through and the symptom returned (wheel stopped on its own after just about half a revolution). Noteworthy at this juncture it kept landing on symbols it had previously lit.
Point being: before the IDC wire reinsertions, the game never would make it this far without stopping early...what do you guys think, did I find the problem with one of the four IDCs on the backbox boards (2 on the CPU & 2 on the Power Driver Board)?
If so, I'll go back and trim the wires & reinsert. Three of the IDCs are 0.10s and one is a 0.156. I've got 0.156s so I'll replace it, but where can I get those damn 0.10s? (Two of them are 9 position 0.10s and one is a 5 position 0.10; prefer to stay with IDC vs. Molex crimp if possible...sources?)
Guess I'll start here and see if I need to do the other 4 wires off the other IDC coming off the Spider Motor PCB.
Thanks to all.