I'll just throw this out there... just because... maybe it'll help someone save some frustration someday

As I was reading this thread, until I got to toyguy's post, this is what I was going suggest too. That thought should never be disregarded in dealing with electronics, ever. It is an idea that most everyone would probably consider, but unfortunately that idea can be dismissed while troubleshooting, way too easily. If the problem does come back again, don't forget this idea is still a possibility also.

(kirkgun is now having flashbacks to some frustrating days of work, long ago)

Always assume the worst of wires and cables. Wires and cables sheathed in plastic are awful and terribly evil things (but don't use uninsulated wires please).

Don't ever trust a "momentary" continuity test (or any kind of "short-term" test) as an indication that wires are good when dealing with an intermittent problem. And by "short-term" test, I mean lasting weeks or months... argh...

Atomicboy,

100% agreed with everything you say. Internal conductor breakage is far less common than at connection points, in any application. Moving wires/harnesses more commonly will suffer internal breakage problems than non-moving ones.

It wasn't common in the field I used to work in either. And troubleshooting them in that field was very often a pain in the butt, requiring running additional "test" cables over long streches. The relative infrequency of the problem made diagnosing that particular problem, more difficult because it way down the list of things we would consider (and there was no outward appearing reason to suspect it). It's just what you have left when your other ideas aren't working. Simply disregarding the possibility, can lead to lots of wasted time/money (and frustration of course, more frustration than anything else with just a pinball machine).

We all tend to look for the types of problems we see most often, first. And that makes sense. It did happen often enough though (often it seemed to be a manufacturing defect of the wire, not something that happened as a result of use). But, as he said above, his problems were coming and going with manipulation and movement. That's why it makes more sense to me in this case than usual.