You keep using the word "crank" when you should be using the word "start" or "fire" for your situation. An engine is cranking when the starter is spinning the flywheel. Doesn't matter if the engine "starts" or not. That's cranking. The battery is not even required for your engine to actually "run" so the electrical checks on that system were, as you found out, a waste of time. An engine that suddenly stops is almost always an ignition system issue. Have you at least pulled the plugs to see if they are wet, dry, oily, etc. If they are wet, that says you do not have a fuel problem. If they are dry you may have a fuel problem. But since you have a spark checker, confirm that you do or do not have spark on all cylinders. The neutral start switch prevents the motor from "cranking" in forward or reverse. It does not kill the ignition system. The KILL switch (if you have one) would kill the engine immediately if the lanyard was accidentally pulled or if the switch itself was defective. If this is a spark issue, then understand that electronics go bad in many different ways. Sudden death, intermittently, once in a blue moon, fail on one cylinder followed by failure on the next, or failure on all cylinders, etc. Yes, a bad module can kill the engine once, let it restart once, and then head off to module heaven.