I had an issue with Netflix in the past, and after my ISP investigated (after I contacted my state's Attorney General's office) they found that something outside the ISP network that was throttling my Netflix access. They had no control over it, and eventually the problem went away. It didn't cause buffering, but did make 4K streaming impossible, and often I couldn't even get 720. So it's totally possible that there's a network issue that is only impacting Netflix. But I don't believe there's anything specific to the Premiere that is causing a problem.
Nvidia Shield, Roku Stick (3600), and Ultra (4640), Insignia Roku TV, Sharp 4K Roku TV, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network. Samsung JU7100 4K TV, Yamaha RX-V583, CenturyLink DSL