Weird appearance and poor rendering performance of point clouds starting from version 1.1

Hi there!

We are now updating our app to Cesium 1.1 and faced a slight performance drop of point clouds rendering, as well as its weird appearance.

Appearance in 1.95 - everything is normal:

Appearance in 1.97 and up to 1.103 - points are to dark and there are some weird artifacts on tiles edges. Performance drops in 10-15 seconds of viewing:

Appearance in 1.103 - points are bright as they should be but there are still some weird artifacts on tiles edges. Performance drops in 10-15 seconds of viewing:

Here is a link to the Sandcastle reproducing the issue.

Appreciate any help on this matter.

Reported a bug: Performance drop with points cloud and apearance issues starting from version 1.97. · Issue #11196 · CesiumGS/cesium · GitHub