Those who stay well-read on the geopolitics will tell you that China's puppet strings are not as strong as we've always assumed. They have used low profile but successive and damaging sanctions on their erstwhile ally over the nuclear issue, to nil effect.
For their part, on at least one occasion the DPRK publicly called out Beijing for essentially being a bunch of western sell-outs. In Asia, between "communists", that isn't friendly talk.