From what you are describing the primers are sticking at the transition from the round primer holder to the tube that feeds them to the dispenser. Try removing your primer holder and look down at that tube. You'll see the tube is in two halves, make sure the 2 halves are snapped together and mating edges of the tube tunnel are lined up to allow the primers to drop through. Also check for small plastic burrs at the entrance to the tube, use an exacto blade carefully to remove them.
Another thing to check is to make sure the tube is fully inserted into the holder. There is a small plastic nub on the holder that has to be covered or else it's not fully inserted. If it isn't fully inserted, a primer can hang up in the resulting gap to the tube and back things up. Good luck, I really like mine.