The Air Nozzle sits on the end of the Cylinder Head to deliver Air to the BB, and also assist loading the BB into the HOP Chamber. The Air Nozzle is an easily damaged part and can be responsible for feeding issues or sudden losses in FPS. It is connected to the Tappet Plate by the groove at the rear, and should have a positive 'spring action' when pressed inwards. Any kind of stiffness to the Nozzle could be related to issues you're having. Nozzles can be made from a range of Polymers/Alloys, and have different degrees of effectiveness when it comes to Air Seal.