Disclaimer: It turns out that his wall charger was wired incorrectly, so mains voltage was wired to the ground of the vehicle, and well the chassis is the vehicle’s ground, hence the voltage. Source. Thanks @WalkingOnEggshells@beehaw.org for the correction.
If it’s 120VAC on the body of the Tesla, I would start by checking the wiring on that charger. The charger’s ground is probably connected to hot. Otherwise, the 120VAC would flow though the ground pin on the charger ground pin, causing the current to spike, and throw the breaker.