First thing I would try is some quality name brand preferably American made ammo. At least at first to break the thing in.
The ammo is even still available at least around these parts.
Could be the Korean stuff is not up to full power and might be a bit crude dimension to cycle properly. It might work after you run the gun some.
We have heard of early feeding issues so I could be wrong. I'd start with small quantities and see if it works.
In Memory of Paul "Dietrich" Stines.
Dad: Say something nice to your cousin Shirley
Dietrich: For a fat girl you sure don't sweat much.
Cue sound of Head slap.
RIP Muggsy & TMan
"If you are a warrior legally authorized to carry a weapon and you step outside without that weapon, then you become a sheep, pretending that JOCKO will not come today."