When you see "plate contact" on the pendant with the Command THC...that means that the torch shield has contacted the plate.....which can happen in a variety of situations. The THC will rapidly retract to cut height and continue cutting (collision avoidance) when this occurs. If you would like....you can shut the ohmic contact function off.
The other issues sound to me like either an electrical noise issue....or a loose connection somewhere between the THC, the Vicon CNCcontroller, and the HPR plasma. I would advise working first with tech service at Vicon, and or tech service at Hypertherm for help solving this issue.
Here is the Hypertherm contact info:
800-643-9878 Tel - Toll Free in USA