ASUS - ZenTalk

I have tried MX player and the default video player app on the phone but the issue don't get any better with any of these. Whereas if I play the same files on other phones using MX player or the default app provided in those phone then too the files play perfectly fine. Also I haven't notice similar issues on the forum or any other third party websites so I doubt this has got to do anything with the software.

It's not so easy to comment without more indepth information. 
What is the video format contained in the mkv, bitrate, color depth, and so on?

For example; trying the "Big Buck Bunny" clip , their 4K 60fps (encoded with x264)  ; http://bbb3d.renderfarming.net/download.html
It works perfectly with VLC and MX Player.  

I will try that file and give you the requested details ASAP.