You’re welcome to call us at the Fellers Tech Support line to narrow this down. I’m going to be traveling the next couple of days and the techs on call support can pin this down. I’m Scott with Fellers BTW. Call 888-863-8383 ext 3120. If you’re not already a customer of ours, maybe you will be afterwards. The nozzles moving around during successive nozzle checks is a sure sign of air in the head.