This problem occurs with the default Rejected Motion in Avatars 3.0.

The default motion is shaking only when affected by others.

Here's a video showing the Phenomenon. The avatar's shoulders and head are shaking, even though the player is not shaking his head.

This problem occurs only with Avatars made by VRoid Studio. This problem did not occur with avatars that were not made by VRoid Studio.

The tracking mode does not affect to be related to the condition of suffering.

This problem can be solved by supposing the strange motion with a different one.

The issue is occurring with Avatar 3.0's default Prone motion.

The default Prone motion only shakes when being watched by others.

There is a video showing this phenomenon. Even though the player isn't shaking his head, the avatar's shoulders and head are shaking.

This phenomenon only occurs with avatars created in VRoid Studio. This issue did not occur with avatars not created in VRoid Studio.

The tracking mode doesn't seem to be related to the occurrence conditions.

This problem can be avoided by replacing the Prone motion with another one.