I just purchase a GLOCK G17 RTF2 FDE VICKERS TACTICAL 9MM. On my first trip to the range it I noticed that I can not close the slide with the sling shot method. The slide locks back on the final round, insert loaded mag, pull back on slide and release and it stops again. Looks like the slide stop won't disengage. It usually takes two or three tries for it to close. It closes just fine when using the slide release. I've tried a couple of different mags and they all do it. Is the spring to strong on the slide stop?