4K Video Keeps buffering

Is this an issue with the drive I’m using (two 3tb in raid via USB 3)? Or the computer doing other things? Or the Apple TV?

I’ve begun backing up my UHD discs to hard drive so they don’t get scratched, and when I watch a video it pauses every two minutes or so to buffer, and this is on a gigabit network.

Is there something I can do to fix this, or is Apple TV just not really ready for true 4K?

Loving Infuse otherwise!