I have "fixed" some of my cheaper moon clips to hold all cases. I use a flat blade screw driver and push it into the slot between case "holes". Closes the fit, holding the case tighter. I tried some and cases stayed in place when dropped from waist high or tossed about 5' onto a carpeted floor...

I'd think there is a reloading error happening that affects chambering "the brass tends to bulge or expand at the base after dropping powder, and seating the bullet causing the moon clips with loaded ammo to not fully seat in the chambers". Too much crimp?