Have had the same issue with my SuperCut50P twice. The overcurrent light and no arc. It is now back getting serviced and have not heard about it for almost a month now. In my opinion, the Supercut 50P is a low end unit, being Mosfit, and the reliability of this unit is poor. Both times I have had issues with it failing, I was not overworking it and I have both a water trap and desicant filters. Like you said, the manuals with it are crap and written by a 3rd grader in China.
I wish I would have spend a little more money and bought a unit with IGBT.