Too much bell! The shells weren't long. The seater/crimp die was catching on the excessive bell. I found the right bell setting and locked it in place with a locking ring as not to change in future. As for seating a little askew every now and then,...the Lee seating die has the adjustable depth for seating bullet. Well, that seating plug is concave where it touches the bullet during seating. For use with round-nose bullets, by default, I guess. My flat nose bullets can go astray on occasion if I am too speedy. Next time will buy round nose bullets. Learned a little bit from this. Grateful only 5 or 6 rounds were wasted. Thank you both for your informed thoughts on the problem.
"Wars are, of course, as a rule to be avoided; but they are far better than certain kinds of peace." - T.R.