Hi,
When you manipulate bone transforms involving Mesh Space Ref Pose Node, you should ensure that you unlock the rotation mode, because you want to override the “main” behavior of the engine. Did you define it to BMM Additive or BMM Replace like in the screenshot below? Check the doc for more details about Rotation Mode.
Click on Transform (Modify) Bone node → Details panel → Rotation → Rotation Mode and select something different than BMM Ignore…The Rotation space of course depends of your Pitch Rotation transform space, usually component space (relative) or world space (absolute).
