For folks having the issue where the round feeds into the receiver and onto the lifter, but does not get brought up into the action.
Two easy and cheap things.
First, replace your stock mag tube spring with a Nordic.
If you have and that one is failing, replace it every few months. What is happening is the shell is not going back into the receiver with enough force to cause the bolt release to allow the action to fully cycle. This spring needs to be healthy for the gun to cycle consistsntly. Also, if you are practicing loading allot, you will wear it out faster. I keep two or three in my bag so I am never short at a major match.
Second, not as critical, get an extra mag tube follower and put it on the top of the spring inside the tube.
What this does is gives the spring good surfaces on both ends so it doesn't bind up as it rotates while shells are fed in, or are cycled out.
Both are cheap and easy fixes.
Good luck