I am having a weird issue with my Hatsan striker Vortex .25. The trigger wont fire the gun unless I slide my finger off the fully pulled trigger and let it just spring back. I have not adjusted the single screw yet but am a little confused about which way to go to pull the striker far enough to allow the piston to go forward and discharge the gun. The first 50 or shots through the gun were ok and then this started happening. Suggestions, or ship it back as a defect?Bob