Hmmm... If it were spring and/or extractor, then dropping the slide with a round in the mag would fail to get it into battery. A simple test. If that succeeds, then you're ammo is too wimpy, or you have a finger dragging on the slide, or some internal hangup. Auto's tend to prefer ammo on the hot side. I don't believe in "break-in period" with modern guns. You don't want to be "breaking-in" something (that would otherwise take one gentle pass with a stone) by firing full power rounds.
For example: The Smith & Wesson 22A is an inexpensive 22lr target pistol. In order to keep the price down, S&W pretends that the tool used to cut the bore is a magic wand. In fact, it tends to leave the bore quite rough. The buyer has a choice; Either put 1000 rounds through it, or spend 15 seconds pushing a patch with a tiny bit of metal polish through the barrel repeatedly from the breech end. Both procedures will turn the gun into a never-fouling tack driver. Which procedure makes sense?