RT-AC5300 and nVidia ShieldTV (gen 2): Slow WiFi speeds

I've narrowed down my streaming issues with my nVidia Shield TVs (gen 2). When connected via wifi, the ShieldTV struggles with transfer speeds (local - from NAS and also Netflix, YouTube etc.); when wired - all is good. I have no issues on other devices (ipad pro, macbook pro, etc.). Therefore, I am very much inclined to think the wifi chip on the ShieldTV is the culprit. This is a 2nd unit I am testing with. Before I think of wires (which in my case is damn near impossible) would there be...

RT-AC5300 and nVidia ShieldTV (gen 2): Slow WiFi speeds