I'm a little bit frustrated to say the least!!!

I have a G540 build that's been working perfectly with the router for months...

I had the brilliant idea of adding a cheapo plasma.....

I read, and reread, everything I can find on grounding, there's a grounding rod next to the table, and star ground system on the table, I have the power supply 0V to ground, I have chokes on every comm cable, motor cables are shielded and drain to ground on the G540 side.

This is a Lotos LTP5000D, pilot arc machine and yes I understand buy Merican, they are better machines, but I don't have $2k burning a hole in my pocket at the moment....

Anyway, the plasma machine works fine off the table, I have relays to turn start the arc, and double relays tied to the tip for probing. Everything does what it should unless the arc is fired in the air, then the G540 craps it's pants..... No matter what I do, I've disconnected every to the G540 but the inputs and outputs, same thing. If the tip is close enough to the work piece, everything works fine, it probes, lights up and pierces, runs a cut, torch off, lights up again, etc, unless the cut goes off the plate, or over a hole....

I bought a Proma DTC and that seems to be working OK, but trying to keep the G540 from dropping out so I can tune it a bit....

PC Never skips a beat, always a the LED on the G540 goes red, torch goes out, gantry dead in the water...

Is there something I'm missing? or Something else I can do?

Thanks for any suggestions...

CR