Apple TV 4 Constantly Buffering

Have had Tablo for about a year now: Apple TV 4 + Netgear R6250 Dual Band router + Netgear Nighthawk AC1900 Range Extender + 5GEXT band.

Worked great up until about 1 month ago. Now any live TV buffers horribly. Have reset Tablo and Apple device countless times with no effect. All other apps (Hulu, Netflix, Curiosity, etc.) work just fine.

Tablo tech had me download RouteThis to try and diagnose. It worked once but tech was unable to find anything. App is now unresponsive.

Anyone have any ideas?