Your problem sure sounds like a spider failure. There's been a lot of discussion on a couple threads that are pinned at the top of this subforum if you want to read further.
Have you had the recall done for the S4 spider? It's a free "fix" at your local Yamaha dealer that takes some load off the daisy chained spider grounding system. This recall hasn't eliminated all spider issues, but has greatly reduced the amount of failures. The better fix was offered by one of our members, but he's no longer making those harnesses.
I'll ditto the suggestions that it doesn't take a complete meltdown to start causing problems in those spider connections. My S7 spider (by left headlight) was showing some meltdown:
Like others, I cut the connector off and soldered the wires together to permanently fix the problem. One of the reasons I did this is because it seemed like the sockets that the spider slides into didn't seem to have much tension and it's difficult to impossible to clean tiny sockets so that the pin going in makes good contact.
Good luck with your troubleshooting. I'm not sure where in WA you are, but I'm near Tacoma and could stop by to help if you're close and want input (although I'm swamped for the next week).
