Yew branches can break your heart! I’ve made some great ones, and some, even after waiting for over 3 years in the whole will do wild things as soon as you hack into them.
A friend made a yew branch bow with me, it was really dense wood, we tillered it out and did all the finishing. A few months later and it looks like yours. I steamed and steamed, used a heat gun, and finally got it straight again. During re tiller, she blew up big time