Hi and welcome to Spine! 😎
Just a programmer's guess: It looks as if you're using non-uniform scale (scale X not equal to scale Y) at the head's parent bone (the bone_girl_neck
bone) or any of its parents, but have Inherit Scale
enabled at the bone_girl_head
bone. This will rotate the head in a "distorted" environment. To resolve this, just disable Inherit Scale
at the head bone.