Contact ARC service.
Just guessing, the manual on/off switch must operate a power on/off relay being held closed electrically by the coil being energized for some reason, or the contacts of the relay are arc welded closed.
Just guessing, the manual on/off switch must operate a power on/off relay being held closed electrically by the coil being energized for some reason, or the contacts of the relay are arc welded closed.

