So the sudden and drastic change in AI behaviour and the fact Scotland's AI woke up doesn't remind anyone else of a reverse version of RTW's save/load bug? Because it strikes me that way - that's why I'm rather desperate for others to take a look.
The scotland/york thing is a side effect of a pathfinding error. They can snap out of it sometimes, even without reload, though i'll try that out to see if it has a consistent effect (if it does, then it's a good thing). On the other hand the rest of the things you mention sounds like VH behaviour where your faction standing has been tanking for 50 turns whereas i think you said you were on M campaign diff. So that is a bit worrying for people who like M difficulty precisely because of the lack of AI "attack the human no matter what" stuff.