According to South Korean newspapers “The governor of North Pyongan Province and was replaced with Mun Kyong Dok, a former WPK official mayor who was close to Kim’s executed uncle Jang Sung Thaek.
Mun Kyong-dok was belonging to the network of Jang Sung Thaek. Mun Kyong Dok was also the WPK secretary of the Pyongyang Committee until 2014.
He disappeared between 2014 and 2017, being not reelected to the SPA in 2014.
Additional information regarding Mun Kyong Dok is available there.
In reality Mun Kyong Dok was sent to the inner country (Jaggang Province) where he purged a three years sentence, being a member of the Jang fraction.