The only thing that stands out at both those time periods is:
ERROR - Error writing media: 10054 - Eine vorhandene Verbindung wurde vom Remotehost geschlossen
Which basically means the Xbox reset the connection, but doesn’t actually tell us why. It looks like the file was Direct Playing the MKV. I have had the error screen popup on the start of playback for direct played MKV’s so I normally leave direct play turned off in my settings so the movies get remuxed out of the MKV container. (But I also don’t know if that is related to to the same you are seeing)