It sounds like the follower is jamming as it passes through the curved part of the mag to the straight. This will happen if the mag body is smaller than normal and should be apparent even without rounds (using a ruler to push the follower up and down).

We had this happen to a USGI mag here also. We took another mag out of the box, put the same follower in it and the second one had no issues.

What type of follower are you using? Gen1 or Gen2?

In short send the followers back for a refund or put them in some mag bodies that work (we have some here we can verify for you).

Edited to add: So long as the mag works with the OEM follower then the mag sill is probably in spec. During manufacture, the testing and assembly of the mag involves cycling the follower the full travel length several times. We sugggest the same test be done when replacing the OEM follower.