A Russian blogger apparently published photos of North Korean artillery shells that had been disassembled. The propellant was clumped and in places congealed on the sides of the shells. This causes the shells to fall short or go too far or explode in the barrel. Several years ago the North shelled an island owned by the South. Only a tiny percentage of the shells hit the island. The rest under or overshot the target by a significant amount. The shells have several issues including poor quality control and the ones Russia is getting are the oldest ones, some dating to the Korean war. That’s problem one. The blogger said some of them had simply exploded in the gun killing the crew.
Are the shells useful? Remember the artillery is behind the lines. If the shells fall short, then they’ll be falling into Russian held territory. (I went looking for this article. I think the publisher was Perun, but he didn’t list these photos in the key words list.)
I seriously doubt your information.
“The (North Korean) shells have several issues including poor quality control”
If I recall correctly, the dud rate was estimated about 15%, with a variety of failure modes - so about the odds of Russian roulette. Most duds probably just fail to detonate on impact.
Inaccuracy due to range variance is probably in addition to the duds.
North Korea is also increasing their new production, but I don’t have a feeling for how significant that is overall.