The UN uses teams of investigators to monitor violations of arms embargoes and regularly releases reports of violations found. In early 2016 one of these reports noted that North Korea was adapting civilian Japanese maritime radars for its warships. This information gives the Japanese another item to block from sale to North Korea. The investigators also found that North Korea was continuing to export light infantry weapons (assault rifles, machine-guns, RPG launchers) to outlaw customers via smuggling routes through China. The most recent North Korean customers were found to be various Syrian rebel groups. North Korea was also found to be illegally providing police training in Uganda and Vietnam. For decades the North Korean police training has been particularly popular with dictatorships because the North Korean teach the nasty stuff (torture and dirty tricks in general) that is generally illegal.
Because of this latest report the United States will again be pressuring China to do more to shut down North Korean smuggling via China. Up until 2012 the Americans were openly accusing China of supplying North Korea's missile program with components and technology. This was discovered in 2012 when debris from an April North Korean missile test fell into shallow water off the west coast of South Korea. Russian, Chinese, and American ships, and perhaps submarines, all joined the search. The water where the debris fell was no deeper than 100 meters (310 feet) making it easy to search for and recover parts of the rocket. Some of those recovered components were apparently identified as Chinese and the Americans used that to get the Chinese to admit they had a problem and to do something about it. China had agreed to abide by embargos on North Korea but Chinese firms are notorious for ignoring their government and just selling to whoever will buy. Ignoring this behavior is not official Chinese policy but accepting bribes to look the other way is a long accepted Chinese practice. China will often claim that things like rocket components were dual use (which could be technically true). In the past China went through the motions of punishing the offending firms but since 2012 has lost patience with North Korea and has increasingly enforces the embargoes and even cracked down on dual-use abuse.
The dual use situation became an issue when the U.S. accused China of selling North Korea a large transport vehicle that the North Koreans modified to carry their latest long-range missile in a 2012 parade. The Chinese truck manufacturer eventually admitted this and said it was not illegal because the truck was designed to haul non-military cargo but, as is the case with many "dual-use" technologies, could easily be adapted to military use. The Chinese manufacturer added that the truck in question was an excellent vehicle and there were many satisfied users.