NK is a wildcard that China doesn't have a great way to get out of. They're just as likely to annoy China for more aid as they are to annoy other countries to remove sanctions.

All of the pathways to a rational NK have outcomes that China would not like including both collapse of the North Korean state, hostility between China and NK or variations on unification between SK and NK. The only stable option is to work with NK too slowly migrate towards a modern Chinese communism approach over the span of decades through the use of aid money, advisors, economic exchange, and educational programs. This only risks periodic regression via purges within North Korea.