I am having a small problem with my XD-9 Tactical. I find out that the slide does not lock back on the last round during normal shooting. I know it is not the magazines as they function prefectly in my two other XDs. Any thoughts on this? I use #19 Wolff Springs in this gun, in case that is relevant, and I use a thumbs locked down grip. As I said, it is not an issue with my two service models.