1. A concise explanation of the problem you're experiencing.
I added an entity using viewer.entities.add and found that there is one extra for the scene.primitives array; but when I use viewer.entities.removeAll(), the extra content in the scene.primitives array is not deleted.
2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.
3. Context. Why do you need to do this? We might know a better way to accomplish your goal.
4. The Cesium version you're using, your operating system and browser.
Cesium1.54 windows64 Google Chrome