PRC has little control over NK whose the one that's been limiting cross border trade. NK would rather starve a few people in exchange for autarky / independance. NK only started openning up to agri imports from PRC / RU in Q1 this year, but that's mainly due to may/june being toughest period for NK agri production - "sprint poverty" right before harvest. All PRC can do is deal with NK like everyone else, while also encourage their missile program since they'd rather NK fling their target at Japan or US West Coast than PRC.