The mag kit needs to be properly spaced from the receiver.
Too close and the mag needs a whallop to get it latch.
Too far out and maybe the bolt isn't picking up the next round?
Next time you're out where you can legally load up your problem rifle,
put a round or two in the magazine and clip it in the rifle.
With the barrel pointed in a safe direction, open the bolt all the and see what
is going on in there.
Gently push the bolt forward and witness bolt to case contact.
Is it?