If both the parent and child have a Rigidbody, they act as . While they may look connected in the editor's Transform hierarchy, the physics engine treats them as two separate objects that do not automatically move together.
If you move a parent using transform.position or transform.Translate , you are teleporting the object every frame. This can cause the physics engine to "lag" behind the visual transform, making colliders appear stuck or pass through objects. collider not moving with the object - Unity Discussions unity collider not moving with parent
If you need the child to have its own physics (like a detachable part), keep both Rigidbodies but connect them with a Fixed Joint . 2. Static Collider Performance Optimization If both the parent and child have a Rigidbody, they act as