Could be the fault ocurrs, when on a cabinet, and somewhat cranked, some techs don't have large speaker cabinets, to test with, might drag your cabinet in, to have him actually see/ able to reproduce the issue, just a thought
Apparently he recently replicated the issue without the cab or cables. It took a long while, but if so, it seems fairly safe to assume it's not my cab. I did ask about the cab and was clearly turned down.