IIRC, the NK’s still have missile bases operating. They are defensive positions, more towards the interior and they are not Nuclear.
Every country has these and they would be fools not to.
NK is dismantling the Nuclear test facilities they promised to dismantle. They are dismantling offensive bases along the border with SK.
Everything is going along pretty close to the terms of the agreement.
P.S. Even if NK and SK form a United Korea, both regions would still need to have defensive missile bases. They would both be under one ‘command’, but why re-invent the wheel (destroy all bases and then build new ones) ?
Just because NK and SK unite doesn’t mean they won’t have enemies to defend against.