You have been given some good advice already, I will add that Harris' hawks will get board doing simple demonstration flights. I worked for a place years ago that did demonstration flights for the public. With our Harris' we would change things up regularly to keep it interesting for him, and it helped a lot. Have the person calling him to the fist hide, and then show up in an unexpected place, make him look for you. Make him fly around things, or under things, anything to make it more challenging for him. With his safety in mind of course. Maybe introduce a lure. I think boredom/lack of challenge is your biggest problem here. Falconry birds are consistently challenged while hunting. Education birds have a much simpler life, and intelligent Harris' hawks get bored easily.