Compute Head Movement from speech not working

Hi - I’m trying to use my puppets with pre recorded audio. Lip sync is working as intended. But as soon as I’m trying to compute head movements the animation isn’t smooth like in the demo videos but jumps every 5 seconds from pose to pose.

Is this a general error or am I doing something wrong? Also my puppet is only a floating head without a body - can this be an issue?

Thanks for the help in advance :)