I don't know this gun, but if it is new, call the factory. Check the instructions on loading the magazine. The most common problem when a magazine won't accept a full compliment of rounds is a cartridge tilting and jamming the follower. There may be a right and wrong way to start them into the magazine. The other possibility is cartridges with too much overall length. Try a different brand or nose style.
If the factory says the behaviour isn't normal, they may send you a new magazine free, so it is worth calling just for that possibility.
Good luck with it.
Nick