Sorry for my misunderstanding, i thought was about standard 4k containers like mp4 or MKV.
Looking to pictures i see you have 1 file for audio track "audio.mkv" (or MKA) and 1 track for video "video.mkv" +
subtitles and thumbnail image.
I see you tried to play the content via SmartShare, isn't ? and seems to be chapters of the same video ..may be tagged in the video track file.
I suggest you to mux the video track with the audio track to a new MKV file, with tools like toolnix, and try to play
the new MKV file in USB 3.0 plugged HDD.
Could you also paste here the content of the text file, i see on the left in the picture, with the same name of the folder please?
Hope to help.
Stefano