Interesting situation, is this real; life experience and does it work on a GFCI?
If so, this is not a ground fault situation and just a false arc problem.
You could try another brand AFCI but I know that is tough if you can't find the elusive "device" and don't want to install a sub.
Personally I would just put a regular breaker in there and say "come and get me copper" if it was my family member who needed the machine. (maybe on a dedicated circuit)
