In 1959, when China embarked on the disastrous “three years of hardship” (the Great Leap Forward), NK seized the opportunity to urge Chinese-Korean graduates and other qualified personnel to take part in the NK Chollima (thousand mile/flying horse) movement, and set up border reception posts to welcome them back from abroad (presumably NK/USSR, etc).China's Great Leap Forward actually began in 1958, but perhaps the scale of the disaster wasn't so obvious until 1959. North Korea's Chollima ('thousand league horse') also leapt out of the starting gate in 1958, and also began seriously stumbling in 1959.
In 1966 when the Cultural Revolution broke out, Kim Il-sung was deeply worried and had no idea what was going on in Mao's mind. But when the Red Guards came up with the slogan, “Chairman Mao is the red sun in the hearts of all the peoples of the world”, started putting up big character posters and said they wanted to arrest the capitalist roader Kim Il-sung [!], he thought to himself, I am the red sun of our country, how can it be Mao Zedong! He was furious and had a martyrs' memorial garden from the Korean war destroyed, including the grave of Mao's oldest son Mao Anying (1922-50).
The NKs set up loudspeakers on the border at this time, flagrantly attacking the Chinese Communist Party and proclaiming, “Chairman Kim Il-sung is the red sun in our hearts,” and even more audaciously building a dam on the Yalu river to divert water and creating a drought in China. The Chinese also set up loudspeakers, attacking Kim as a “Korean revisionist”. This was the doing of the Red Guards and “rebel faction” while the official media kept quiet, but relations between the two sides atrophied.
Kim later saw what chaos the Cultural Revolution had created and how the “capitalist roaders” in China had been overthrown, so when he visited Beijing he apologised to Mao and admitted his mistakes. He promised to rebuild the martyrs' memorial garden, while Mao said friendship came first and mistakes were secondary.