See video for reference (Canny doesn't support attachments higher than 8MB): https://youtu.be/iRIyLLPYOEo

Basically, there is a bug where if the Phys Bone chain has a radius at the beginning of the chain that is too small, it's behavior to colliders will cause ugly jittering. This is especially evident regardless of Full-Body Tracking.

To fix this issue, the Curve must be modified to ensure the start of the chain is larger than 0.1 in the test.

For clarity, the Phys Bone chain affects two transforms with a custom endpoint position for the Radius values to be visible. This is most common for Avatars with feminine breasts, especially to save on Phys Bone count.

This was tested on both Live Build 1802 and Open Beta 1815.