Earth Continuity Test - Current Through Probe?

[TeslaTestAndTag]

I noticed some sparking coming off the probe during earth continuity tests on class 1 devices when the probe is touched to the metal casing. I placed a clamp meter over the probe and got readings of up to 10 amps. I can also feel a vibration from the probe lead during the earth c test. It's almost as if the tester(Metrel 3310A) is pushing amps through the probe lead on to the casing of the device rather then pushing it up through the earth wire in the lead to the casing?

Any idea of what might be happening?

 

[ohreally]

An Introduction to PAT Testing - YouTube from ~ 40s onward.