I had a similar problem with some King Arms magazines, but a couple drops of silicon oil in the empty mags, fixed them for me.
You said you have lubed inside the mags, don't know how you did it, but try dropping a couple of silicon oil in one empty mag, then load it to spread the oil and finally fire the gun to test it.
Another problem with king arms magazines, particularly the metal ones, reported
here is that the retaining lip that stops bb's from flying out is a bit too long and you might have to file it back slightly until it feeds correctly, but be careful not to file too far or you might damage your mags.