Shell stuck in die
I had a .223 Remmington Hornady sizing dies that would stick a case 1 out of 10 times. I bought an Upgraded set of .223 dies. As soon as I did, I sent the dies back to Hornady to have them polish the inside of the die[s]. No more trouble.
I have gone through several different lube greases. The only one I can get to work, to my satisfactioon is Hornady's UNIQUE GREASE.