MKV rip of a 16x9 movie doesn't fill the screen on XBOX one (or XBOX 360 for that matter). Plays fine on PC, phone, and tablet.
Used MakeMKV to create the MKV file.
Get black bands on right and left of video as well as bottom and top. I expect boarders on the top and bottom, not horizontally on the left and right.
What version of the server are you using?
This bug normally happens when you pass anamorphic videos through the transcoder. Currently, all MKV's being sent to the Xbox One need to be remuxed as support for direct playback MKV is being added in the next update that is currently still going through the certification process.
If you post your Plex Media Server.log or look inside of it when you start the video playback you should see what exactly is happening to the video.
