When stacking 8 switches, all of them *unconfigure switch all* and out of the box... So they have never had ANY CONFIG. Some switches show this when you run show licence
You see Feature Packs: DirectAttach
This causes members of the stack to fail to join with a licence error. Not sure what DirectAttach is or why its installed. But I had to do a clear licence on all switches before the stack would be stable at all.
I guess one or two of the switches didn't have the direct attach license. I couldn't find much literature on it, and I found clearing the license allowed me to build the stack without any issues whatsoever.
I want to say I remember something changing with this license, to the effect of it being available without a license in this version, but I don't remember the specifics right now. When I get to the office tomorrow, I can ask around.
Hopefully one of my colleagues can hop in to my rescue before then though