Earlier quoted context omitted.
> NK isn't some rationalistic actor. I don't see why you say this. I wouldn't say they are especially competent, but they seem to have stayed in existence and played off various larger rivals successfully for 70 odd years.
Put another way. They're not going to play ball. Things cannot be solved diplomatically. Unless you call breaking all diplomatic promises, and developing nukes diplomacy. A rational actor is a nation that is predictable, and is willing to uphold their word, and agreements. If promises are broken, agreements torn a part I don't think that state is a "rational" actor.
North Korea acting unpredictably and dishonestly has little inherently to do with the rationality of those actions, and there are strong arguments to be made that those actions are rational from the perspective of the North Korean ruling class.