Straight arm hanging scapular strength is often overlooked and a common cause of shoulder pain, at least per my clinical experience. We tend to underestimate the stress being put on the shoulder while in the hanging position. If you think about it, when loading barbells or lifting weights, we gradually increase the weight. However, with body weight movements we cannot just chop off a limb and then re-attach. Jumping up to the bar and hanging with full bodyweight is often too quick and large of a stress on a shoulder that has never been in that position before or for an athlete coming back from injury or experiencing pain.
Check out this video on different loading methods for the shoulder in a hanging position. It starts from hardest to easiest.