My multimeter says 2KV DC. I'm not sure I can trust it.

I understand that Ohm's law doesn't allow this condition. 2KV across even 1Ohm would give 2,000A of current flowing through the PSU case and some wires that only handle around 4A.

I'm sure all of the ground points I've checked are connected by low impedance.
There's no excess heat or melted wires etc.
My components haven't fried despite apparently having hundreds of volts difference between their grounds.

The only conclusion can be that there isn't really 2KV. There has to be something though as my circuits keep resetting and the multimeter is showing such high voltages.

Is there anything I can do to help narrow it down? I will try the 1MOhm resistor idea to see if it makes any difference.