After upgrading to Cesium 1.10, I noticed a weird flickering that happens when we move the mouse around the canvas.
It only happens in parts of the canvas where drawing objects in top of black background (either the space/stars area or the globe with the terrain layers disabled, like in the picture).
I suspect that this happens due to use of drillPick() method every time the mouse moves
The above pic displays the flickering. After I enabled terrain rendering, the flickering disappeared except in the the two shapes that have part of them on top of the stars/space background (and even then, there was no flickering in the parts that are not ‘in space’).
This also seems to happen in Cesium 1.9, but seems more difficult to reproduce there