The only thing I can think is that it was the TVOS upgrade in Feb? It all worked well when I got it and that was the only thing that changed, I haven't switched modems, routers, etc. So I get the new box yesterday, set it up with a wired connection, speedtest, same crappy results. I even got Apple to switch out the box since maybe the ethernet port failed. So I got a brand new CAT7 cable, called apple support, reset my Apple TV, all the things you would expect. Now I prefer wired ethernet when possible for speed, performance, etc. So I switched to Wifi and speeds are up in the 40 range, a huge improvement and I eliminated the buffer. Now, let's test the above setup speed, from TrueNAS to my Mac running on Big Sur, I will copy a 5GB file to my local drive through a 1Gbit LAN opening my Mac has: Code: rsync -a -progress -stats -human-readable media/Movies/8\ Mile\ \ (2002\)/8\ Mile.mkv. Ethernet is often 6 times faster than wi-fi.
I have the 200 speed package from Time Warner and this was never an issue before. If the backup is on a Time Capsule or OS X Server, connect with an Ethernet cable if possible. and Media Access Control (MAC) parameters must meet. So I ran a speedtest and i was getting 1-2mbps on a WIRED connection. 400GbE refers to the next capacity rate in Ethernet interfaces that can travel through a single. It's odd because Netflix usually works well even on slow connections.
A few weeks ago I noticed buffering issues on Netflix, which never happened before. I've had the AppleTV 4K for about 5 months without any issues.