First we take a risk at buying a newly release Airgun to market, secondly both FX airgun have been reportedly have small issues with multiple owners. With that said I hope that all the issues are resolved in a timely manor, none of which helps you, it should just be consider food for thought. Pellets are not clipping so that is good. To check leaks are EASY, fill up the tank before bed write the number down and check it in 12 hours. POI shift is different, I would first do 10 shot groups at 25 yards and see how it groups (30 shots). Fill it up and do it again and see if there are any POI shifts at 25. I would make sure that your scope is tight but not overly tight which could damage the lens and play havoc on your shooting. Shooting from a dead rest doesn't mean you are going to have .5 inch groups if all your technic (hold, breathing, cheekweld, and trigger control) are not good. I believe you mentioned you are shooting JSB 16 or 18's both are fine for these testing, and the only reason i say that is Most guns shot them well, not all guns but most. You may have one that prefers H&N's. If you can get .5" groups at 25 yards all 6 shot groups then move back out to 50 yards. Baby steps work for me in narrowing down problems. and now you think you have a leak, and second point of impact is changing. Please post a target group next time if you can, and have you Crony a shot string yet? If not you really should see what your gun is shooting at if you are blasting away over 1000 FPS that could be your problem, or below 800.