I recently ran into an issue with CESIUM where I was getting phantom data to appear inside CESIUM. This issue is caused by the fact that I have a series of one or more points, an multiple polygons. What was occuring is that I would draw an ellipse on the globe using the CESIUM.Shapes.ComputeEllipseBoundary function, and then switch ellipses (delete the original ellipse and create a new ellipse) the old ellipse would still display inside of CESIUM. Specifically the old ellipse fill/shading would display within CESIUM but no border. The issue also only occurs if the new ellipse encompasses the original ellipse. Thus the user would see an ellipse inside and ellipse where only the newly created ellipse would have a border to it. I verified that original CZML object was indeed removed from CESIUM prior to the draw of the second, larger ellipse.
I believe the issue is caused by my other points. My other point CZML objects had polygon settings applied to them but no polyline data. Essentially they had polygon settings of show = true, and interval, and a color with a transparency value.
After I removed the polygon settings the issue went. I wanted to submit this behavior since it seems like an issue that could be addressed within the CZML codebase.
I have seen this issue and B16 and B21. I have not tried to reproduce the issue on the latest version of CESIUM.