Hey All
You missed an very small but important component. Your ignition TOGGLE SWITCH. Change it out. Get a slider switch.

A couple of years ago, I had the EXACT SAME problem. It drove me nuts. I replaced the toggle switch on a hunch (I had NOTHING else left to change!!!). Lo and behold, the problem went away.
Toggles are not the best switches to use in my opinion in any RC application.

Cheers
Henry