mp4 Files studder on my Gen 2 WD TV Media Player

I have been searching for a solution everywhere and it seems as though quite a few people are having the same problem as I am.  mp4 movie files (720p or 1080p) studder.  I tried it on my friends gen 1, works perfectly, but not on my gen 2.  I coverted the mp4 to mkv and the studdering is gone but for some reason I can’t transfer the audio. 

If there is a solution to my problem please let me know.  I don’t mind converting my mp4’s to mkv’s if thats the only solution to stop the stutternig, I just need to know how to transfer the audio with it.

In conclusion:

1.  Is there a solution for the mp4’s to stop stuttering  OR 2. transfer audio over to mkv when converting it from an mp4.

Thanks again for all the help.