For avian reasons Namelisd does similar. My fingers, hand, stick, etc turns into bird eating torture devices. That's normal and irritating showing of independence. Remain calm. Plan your actions in steps with your end goal. The cage is his territory. You don't desire him to become progressively aggressive. If you want him out or you to reach in work with it. If he's going to attack the stick, just hold it there. He'll learn/see you don't care. I've had Nameliss all but the first few months. At 21 she's does what you're describing randomly. It gets worse when she's hormonal. Patience, consistency is your best friend. Birds are prey animals. They know it instinctively. If flight isn't available then aggression is their option. Plan your actions around that. If his feathers don't tell you much, watch his eyes. The pupils will rapidly contract and expand (pinning) with excitement positive or negative. I bet Yvonn is normal CAG intelligence. You've shown him another cage opening to explore and exploit. I have heavy toys hanging at cage top opening. Nameliss worries it until the fastening becomes loose. Then the top becomes a safety factor. So be careful.