If you are sure that all wiring is in good condition and safety switches are good, I would get a new start relay and replace it, as relays can be affected by heat. If the problem still occurs, put the old relay back in and replace the kill relay. Replacing one relay at a time, just saves you buying two relays. I’ve only seen both relays going bad at the same time, once. If you want, you could just replace both from the start, just a little more $$$$. From your description, those are the only parts you are uncertain about. Spark plug wires have nothing to do with your problem, totally different electrical system, so cross that off as a possible cause. We both don’t know how the tech tried to solve the problem, but I would like to know if he tried different relays after bypassing the safety switches. This should not be a hard problem to solve, if the tech follows a good electrical troubleshooting procedure. Electrical troubleshooting can turn ones hair grey and cause one to drink, but with patience and a good understanding of electrical principles, plus a good procedure it can be done. If you like the unit, I would find the best electrical guy around, brand does not matter, and ask him if he would give it a try.
