[Bug Report] set_external_force_and_torque bug

[JunghwanRo]

Describe the bug

Bug initially identified With the quadcopter example for Isaac Lab,
(IsaacLab/sources/standalone/demos/quadcopter.py)

Force only applies to one of the rotors, after

If you change the name of the quadcopter body in Isaacsim,
from body -> any name,
and set it back to
any name - > body.

I've checked the difference of the .usda file after this; the only difference was the location of the body definition.

Later, while developing a morphing quadrotor env., I bypassed this issue by
finding correct rigid body ids used when calling set_external_force_and_torque function (by observing in the simulation)
and manually modifying the body ids.

Steps to reproduce

Change the prim xform name
body -> any_name,
and set it back to
any_name -> body.

System Info

Describe the characteristic of your environment:

• Isaac Sim Version: 4.0.0

• OS: Ubuntu22.04
  Both happen on CPU & GPU

• I have checked that there is no similar issue in the repo (required)

• I have checked that the issue is not in running Isaac Sim itself and is related to the repo