Hi,
You can’t set a camera position of a tracked entity, as there’s a controller for the camera now that will interfere with your forced values. If you want to control the movements of the camera of a tracked entity, I suggest you don’t use the Cesium tracker, but make your own that you can control. You hook into the Cesium render cycle, and move the camera according to the entity the way you like it. More on this at the following links;
Own tracking; Tracked Entity + camera heading - #7 by Hyper_Sonic
Specific angle; How make camera follow tracked entity from behind?
Restrict moving around; Do not move camera when setting trackedEntity - #3 by vrana
Cheers,
Alex