[cabmandone]

If he struggling, walk away from it, do something else. His issue could be he didn't sleep well the night before or his arms were tired from doing something else. Maybe the focus just wasn't there.

Something to watch for, make sure he's not "torqueing" the bow. In the pic above, the bow looks straight up and down. Make sure he's not gripping too tight and causing the top or bottom to tip out. You want the bow to be pretty much straight up and down.