1. A concise explanation of the problem you're experiencing.
PolygonGeometryUpdater.js
line 346 and then
DyanmicPolygonGeometryUpdater;
4. The Cesium version you're using, your operating system and browser.
Cesium 1.55
Looks like you’re right. Feel free to fix that yourself if you’d like to open a PR and be an official contributor!
Contributing guide: https://github.com/AnalyticalGraphicsInc/cesium/blob/master/CONTRIBUTING.md
Thank you for your advice.
I will read the guide carefully.