I think all anyone could say here is this:
the netflix app works for most people as designed, thus you're running into an issue where you need to ensure everything is updated, app and windows, and that you don't have a lot of background programs open. reinstall the app, and you could even reinstall windows. close AV and see if the problem still happens. whats the difference between your machine and a brand new machine they tested it on? one of the differences is causing this.
you could try watching it in the web browser as well, but you could already have your reasons for not doing that.