Audio missing in some downloaded mkv files

Some videos I download in "mkv" format (since I need to download 2k or 4k format) have no audio (have video but no sound).
If the same video is download in "mp4" format, audio is present.

This usually happen for newly added files in YouTube. If I download the same video in "mkv" format a few days later, the audio may be present.
At the time of writing this problem, following video have the problem mentioned.
http://www.youtube.com/watch?v=1RYo3bHFRwY