Sony XBR850D tv, 10Gb fiber connection from my FreeNAS box to my nighthawk x10 wireless AD router, with the Sony set to wired or wireless - I can't play a 65Mb/s 4k video without constant buffering, set to direct play. Using ARC over HDMI, router is in the same room as the Sony, so wireless should be 1Gb +. The native Sony video app plays much much better, but still buffers every once in a while. My samsung Tizen tv upstairs is way further away from the router (wireless) and plays the same video (direct play) flawlessly, never buffers.
I'm wondering if it has something to do with the audio track (maybe it's DTS?) causing the Sony to transcode and the freenas box just can't keep up with transcoding.. or is this a flaw with the plex app for Sony android? I'm very close to taking this back to get another Samsung.