Hello. I own a new ASG CZ P09 GBB pistol with polymer slide. The problem is that it can barely fire 3-5 shots before short stroking and then venting all the gas in the magazine. Even at the first couple of shots you can see the gas escaping through the slide and the pistol gets cold almost instantly. I have sent it back at the retailer but they did not help as they insist there is no problem with the pistol. I have tried different magazines, shot it lubed and oiled, shot it dry, changed the nozzle along with its o-rings, nothing changed. Can anyone suggest a possible solution? Thank you.