Camera-following body does not actually bend relative to camera

Hi! I am working on character animations, and currently am struggling with head and body animation.
Normally, changing C0/C1 of the Motor6D can change the rotation of the body parts properly with the condition that the front surface of it must be facing forward like the player’s camera. Otherwise, the body part will accidentally misalign to the left or right like my situation:
robloxapp-20230827-1651073.wmv (1.1 MB)
Is there any ways to rotate the torso without depending on it’s orientation, like depending on HumanoidRootPart’s Cframe or something similar to it?