Ring Wave Test

I have never seen one of these setups, but I very much doubt this is normal; any responsible manufacturer would have at a minimum put a warning label on the equipment regarding the safety hazard of flying cables!

From what I can see of the spec sheet, the output current of the generator is supposed to be resistively limited. I suspect an internal breakdown that is bypassing the resistance. Another possibility is that the test connections are incorrect for the chosen parameters, or there is a ground fault in the test cabling or UCS500-M. Review the instruction manuals. If the manual is ambiguous on any point regarding your setup, contact the manufacturer's product support.

If you don't find a problem with your setup, then it's time to check the equipment. Disconnect the equipment and inspect everything inside and out for signs of arcing. Pay close attention to any place where high-voltage cabling goes close to metal structure. I once found an intermittent RF power generator problem that left a small pile of powdered insulation where a wire rested on a resistor terminal (repaired by moving the wire and patching the hole in its insulation).

One other thing just occurred to me: is your test setup near a large-area magnetic field? For example, is there a big transformer or motor on the other side of wall? Stray magnetic fields can produce unexpected motion in wires carrying significant currents.