In the back of my mind is something 'filed' about that ammo being iffy on QC, lot to lot and it doesnt surprise me.
I assume it chambers up just fine? Try wiping each case down with a cloth to ensure there is no luby residue on them, and swab out your chamber.
You might also try the 'BB trick' from the FAQs for the ejector (and since it would be apart do the whole ejector tune too).