First thing I would check is that little tab on the upper surface of the bolt release button that interacts with the latch trip.. If off a bit (angle) it can do what you describe..
In any case, IMHO the problem is in that area - between the release button and the carrier latch system..
I had the same issue. The tab on the bolt release button was not playing nice with its interacting piece. Was looking to replace it anyway with a longer release button. Took three hands to get it back in but, problem solved.
