Repeated buffering at end of 4K movies - even with Directplay

I realize that Plex wasn't designed to stream 4K movies, but it doesn't make sense why it would stream perfect for 2 hours and then crap out at the end.

Specs:

Xbox One X streamer

1g internet hard wired

​

Streaming box:

9900K @ 4.8ghz

8g DDR 4 @ 3.3ghz

Plex set to hurt the CPU on transcoding

720 seconds of buffer

NVME M2 drive is setup as the temp directory, with hundreds of gigs of space free

​

Any thoughts? Increase buffer to the entire movie?

Submitted by isecretlyjudgeyou | #Specialdealer Special Offer Online Shopping Store 2016