Once I had a bunch of squibs with 45 ammo reloaded with W231. Missing charges and low charges. Loaded a batch while watching the charge bar on my Dillon 550 cycle every time. Still had squibs. So I emptied the powder hopper to see if the powder was at fault. Nope. The problem was a moth lodged in the outlet of the hopper partially blocking the powder flow! How it got there haven't got a clue.

Might be the issue.