Afaik, most of the NK artillery lining the DMZ is buried deep into hillsides
You still have to get it outside to be able to use it. Once outside it becomes traceable to MLRS.
Existing pictures of North Korean artillery show an amazing variety of muzzle flashes from identical guns. As they are still using 1950s ammunition I would be surprised if all of it was serviceable.
I can imagine a large proportion detonating in the barrel, falling short or very short or veering off in various directions.