Double clicking or clicking the camera in infoBox for an entity in fixed reference frame tracks the entity by locking it to the center of the map. However, when I switch to inertial reference frame, it does nothing and does not track the object. There are no error or messages. So does tracking entities work at all in inertial reference frame.
Here is my sandcastle. Cesium Sandcastle
You notice it shows the satellite ISS for both FIXED and INERTIAL. But it only tracks for FIXED.