If it were a 3w set up where the neutral and EGC share the same conductor I would confirm the integrity of that wire back to the panel. If any the connections this conductor are compromised and 120v loads that are L-N can provided the opportunity for current to pass through a person who is touching the appliance and a grounded item at the same time instead to that current returning by way of that neutral/EGC conductor. If this is the failure then it substantiates why a separate neutral and EGC are superior.
