A common mistake, especially when trying to create more range than flexibility allows, is to bend/round/arch the back. The shoulders come forward and the upper part of the thoracic spine is crunching.
This is not a mistake, nor dangerous if done under the right conditions, but in a hip hinge, this is not part of the exercise’s goals.
Keep the back straight by remaining focused during the exercise. Pull the shoulder blades slightly down and together to push the chest out and keep the shoulders back.