The trouble in the RC North sector is afaik concentrated on Pashtu minority regions.

You can have all the hearts and minds of most settlements, but meanwhile there are a few Pashtu settlements in between whose inhabitants feel suppressed by a corrupt non-Pashtu governor. The Taliban arrived and slowly gained footholds over the years.
Meanwhile, ANA and ANP units that prove to be useful in the North are sent as auxiliary troops to hot spots in the South. This guarantees that no matter what the Western foreigners do in the North and no matter how ready the mayor of Kabul and his clique are to take over security responsibilities in the north - the assistance mission cannot end before the hot spot fires elsewhere are extinguished.

The North could be more quiet, but no matter whether it's quiet or not, it's simply not decisive. It's a sideshow.