First step, the panel. Took a torque screwdriver through the panel tightening every ground and neutral with a wire on it.
I know you think you have a calibrated arm, YOU DO NOT. It is a wonder this is my only problem. I'm going to change shoes and do the hot wires later after what I just saw. I probably should have worn my insulated boots for the entire panel now that I think about it.
All tight now including confirming the specific ground for the faulty circuit. Tested, still voltage on ground at the outlet where I found the problem.
I guess that means I'll be opening up outlets and light fixtures. Yay