Talos docs

spring-bone-unknown

Since 0.7

a chain or collider names a bone the skeleton does not have (the message lists the bones it has), or the entity has no skeleton to swing (no animator, or its asset has no skin or did not load)

Plain text
Severitywarning

Meaning

a chain or collider names a bone the skeleton does not have (the message lists the bones it has), or the entity has no skeleton to swing (no animator, or its asset has no skin or did not load)

Fix

use the rig's own bone names; give the entity an animator on a skinned model that loads