Hi Wingman
Here are also my logs from playing ( hw transcode )H264 4k video from my 4k DJI cam.
Checked with v. 1.18.7.2318
I am playing it on UHD Samsung TV.
Video is freezing and extended time loading, sometimes also blurring
As mentioned also user brycegturner. (same NAS)
I put also screenshots from NAS performance, I dont see there much traffic, even I heard that disk is working hard 
Another topic is that I tried to stream it with Windows Media DLNA via my notebook.. and video was almost smoothly, but I figure out that bottleneck is TV ethernet LAN 100Mbit,
and the I just realized that all 4k TVs are branded just with 100Mbit NIC, even on 2000$ TV !!! what I read on web.
