The issue (maybe) is from going inside to outside. The temperature rises, the pressure rises. Empty and go outside and shoot. Or if you have a test setup inside and a pellet catch. Fill inside. Shoot inside. I'll bet the first shot is normal. Same as if let the gun get up to ambient temp, filled (from empty) and then shot outside. Once the temperature rises from either walking outside with the gun, or walking from the car to the range. It's gonna stay there until you shoot, or allow the temperature to drop. The expansion happens In the reservoir and plenum. Or do you mean you could be out shooting and everytime there is a decent pause you get drop off?