Out of spec. - L2D Combat Upper Parts Kit, Glock 9mm

L2D Combat upper parts kit SS. Issues with the firing pin assembly. Slide moves 1/4 inch rearward (out of battery?) when trigger is pulled and release strike 50% of the time on both Swenson G17 slide and OEM Glock 34 slide with OEM cover plate, OEM recoil spring and OEM Barrel. Replaced striker spring with both OEM and reduced lone wolf reduced power striker spring and slide functions 100% - No movement of slide when trigger is pulled. The supplied striker spring causes binding of striker/firing pin , however L2D Combat striker functions 100% with stock OEM Parts. NOTE: kit does NOT include COVER PLATE.