Bobbo, I know it seems like we're beating up on you, but we're not. I appreciate you presenting the case in the first place as a troubleshooting problem. Good stuff to challenge the mind.
But, I agree with wnjj,
wnjj wrote:
Either you did without knowing it or something is still wrong.... I'd make really sure something still isn't wired wrong, intermittent or reversed.... Unexplained symptoms always indicate a misunderstood problem.
I also have many years (>40) troubleshooting electronics. What wnjj is saying is don't give up, don't assume anything, and don't fool yourself.
Who knows - It very well could have been something out of left field like a overtightened cable clamp that shorted wires together or to the box, and that connection is mechanically intermittent - clearing itself at the most inopportune time. Ask me how I know - I had that happen energizing a whole metal sunroom frame. It wasn't discovered until a year later when the weather was cooler and things contracted, and someone grabbed the frame in bare feet. All the outlets in the sunroom tested and worked fine.
Something just didn't add up for the symptoms you originally reported.
But, thanks for the challenge...