The time I experienced this exact thing it was because the hot and neutral wires from the line cord were switched when it was replaced in the machine. The house did not have grounded electrical. It was explained to me as the line filter removes RF interference from your house wiring which acts like a big antenna. That excess current goes to ground which went nowhere with an open ground.
Swapping the hot and neutral wires to where they were intended to be solved it. So I guess one thing to check is grab your meter and make sure the hot and neutral inside the machine go to the appropriate pins on the plug.