I have a syncrowave 250 dx. I'm running on dc- every once in a while when I press the peddle to strike an arc my arm that is resting on my work bench will get shocked. It's extremely annoying and I can't figure out why it does this. It doesn't matter whether it's my torch arm or the other. And it's very random. I can't seem to find a pattern. Does anyone know what might be causing this?