MKV files don't play on RP2 but do on PC

Hello All,
I have SOME MKV video files that give “sad face” when I try to play them on my RP2 Kodi system.
Other MKV files DO play OK and the offending files will play OK on my Linux PC Kodi system.
Can’t figure out why.
Info on systems as follows:
OS OpenSource 2017.08-1
Kernel: Linux 4.9.29-11-osmc
Video: GPU VideoCore IV HW
OpenGL version: OpenGL ES 2.0

PC Linux Desktop Gateway
Kodi 15.2
Ubuntu 16.04 LTS
Kernel: 4.4.0-96-generic

As I said most MKV files play OK on the RP2. Just a few (from same source and same TV show “Narcos”) but do play on the PC

First thing I think of, have you purchased the codecs?

To get a better understanding of the problem you are experiencing we need more information from you. The best way to get this information is for you to upload logs that demonstrate your problem. You can learn more about how to submit a useful support request here.

Thanks for your understanding. We hope that we can help you get up and running again shortly.

Also, It would be best if we could find out more about the file you are having issues playing. Please see the mediainfo section in How to submit a useful support request - General - OSMC