I've done everything I can think of outside of the control box. Cables, motors and encoders are fine. I've rebuilt the cables totally ,( power and encoders) checked, checked and checked wiring on the terminal connectors. We had a tornado back at the end of summer and the power went nuts around here for a couple of weeks, as the crews were out pulling trees off lines and such. All my grief seems to have happened after this - I don't know if the events are related or not. Makes for good drama though.
It is likely something inside the control box, but I'm walking away from it for a couple of days - just to clear my head. I don't tend to get into a hurry firing things up anymore. I usually walk away, then come back after some time off then look over things again: find all kinds of kinky things.
While the equipment is down, I'm building a new, swanky looking control box, (I've been sitting on some swell aluminum sheets for a while). New SS relays (I just got some cheap), barrier strips, lights, knobs, wire, extra wraps of bindertwine, library paste, etc. and anything else laying under the workbench. Reinstall Win2000. (why not? it'll build character if nothing else)
While rebuilding, I will do as you say. Test it precept upon precept, line upon line, pin by pin, wire by wire. Doubtless, as it always is, something will show up that will make me feel stupid.
If nothing else, this will give me time to learn how to use Rhino.