As above. When cycling a round in the chamber never short stroke the slide. Always pull the slide all the way back and allow it to snap forward under all of the spring tension. If you slow it down in any way it could hang up. As to your current issue. My guess. The gun is newish. You wanted to place a full magazine into the gun with one n the chamber. In this condition when the slide is retracted it drags on top of the round at the top of the magazine. The magazines may need to wear in a little. The spring may be a little tight. Not uncommon. I think after you shoot a couple hundred rounds this will go away. Just use one less round for now until everything wears in a little.