Unexplained flyers? No, those are strays.
Strays are easily explained. Seriously.
Try this, it'll be slightly different from y'er normal routine.
Instead of just loading mags as fast as possible,
or grabbing from the box to chamber the next shot quickly,
use Mark I eyeball and look at each cartridge individually.
Pretend it's one of y'er center fire handloads and critique the cartridge.
Is it visibly uniform in appearance, or can you differentiate from the next/ previous cartridge? Why?
Does it show identifiable scratches, dents, dings, chips,
variations in drive band widths, groove widths?
Is the bullet seated square to the case mouth or show angled seating?
Most important, is there bullet material compressed down past the case mouth on to the brass.
Start inspecting your rimfire cartridges before using, those strays are easily explained.
Would you expect a 223 that looked like it was dropped on the deck, kicked around for a week, picked up and chambered
to fly the same trajectory as the rest of it's brethren, pristine from the loading press?
This is bulk ammo we are discussing, most of it looks like it was beat to snot
while being assembled on the production line.