You probably need to disassemble and clean the die. You can have this problem with properly lubed cases if you've switched lube types or the die gets a little gunk in it.
It doesn't take much to make things stick.
Scrub it out with a bore brush and hoppes #9, dry patch until clean, spray inside with a bit of the same lube you're using with your cases.
Should be good to go.
I had this problem with a 25'06 NECK sizing die. I stuck 3 cases in the thing before I figured out what the problem was. Visually the die appeared clean, but after I scrubbed it, no more stuck cases.