I'd also take a few minutes to check the plug wire for #5. Resistor wires break down over time.
I can't recall the exact resistance per foot but a quick check would have it read somewhere between the resistance of #6 wire and #4 wire. When checking it work the wire around a bit with the meter leads connected. A break will sometimes show continuity and vice versa when a wire is twisted into different curves.
Could also be as simple as a bad plug too.
