The problem with the Mark 5 500 blade wobble has been fixed.
I have a pal that is a locomotive machinist. He came by. He read every post. He went out and Cranked on the arbor nut. It was loose, way loose for an arbor..... crap.
I am a wheelchair guy. Yeah, I am running my ShopSmith pretty much in my powerchair. I am not as strong as I once was. It sure felt tight to me. Every lock was well.... loose. Lessons learned. It also demonstrated a bit of runout, not bad but...The combination of variables add up. That arbor is NEVER coming off that blade.