Craftsman Riding mower won't shut down when hot.

I Have an older Craftsman 10 HP 30" rear engine riding mower. The mower starts and stops fine when the mower is cold, but after a few minutes running, the mower will not cut off (either by Ignition switch or by safety cutoff).
The mower will cut off fine until its been running for about 3-5 minutes.

I have replaced the ignition switch (No effect)
I have measured the ohms from the kill wire to ground and it is not grounded when the mower isn't able to stop normally.

I am thinking it may be a bad system ground (but the system ground is 8 inches from the engine, why would running 5 minutes make the ground fail???)

I have torn the mower apart and tested all the safety switches and wiring, and I can find no switches that don't work nor any skinned or broken wires.
Any advice would be welcome.

Jcrowder3

Craftsman Riding mower won't shut down when hot.