Its likely that the case mouth was slightly crimped and the case mouth itself was rough. Both will leave a bullet seemingly welded to its case. Kinetic pullers are nice and work well enough most of the time. But a good Colet style bullet puller will never fail you.
New cases need attention too. When I buy new brass, there are a couple things I always do.
1) They get a quick cleaning, 15 Min's in the tumbler.
2) They get their flash holes deburred inside.
3) They get FULL LEGNTH re-sized.
4) The lengths are checked & trimmed as necessary.
5) They get the case mouths deburred inside and out.
6) Another quick tumble to remove sizing lube.
I realize what I do is not mandatory, but when I'm done, I KNOW the cases are ready for any loading I will do.
CW
EDIT for spelling.