I just took my new 1911B to the range today and went through 150 rounds. On four separate occasions the slide did not lock back after the last round was fired. When this occurred I manually locked the slide back and the magazine was difficult to release. With the slide back on all four occasions, when the magazine did manage to disconnect the slide released. I did a full takedown and clean before taking it to the range, is this merely break in issues or is there something I should have looked at? Thanks!