I have a rather old Miller Dialarc and if I press the off lever it wont catch or something and i have to push it down several times or just unplug it, but it will stay in the on position just fine. What could me problem be?Miller Dialarc 250Miller Bobcat 225Hobart Oxy/FuelCouple of Dewalt and Milwaukee GrindersJET Bandsaw and Drill Press