Unable to connect to Content Server

I have about 65 movies on my newly installed Plex Media server.  All of the videos play perfectly via the Plex Web interface on Safari.  When watching via my Samsung TV using the Plex app, most of the videos play without problem, however a few of the videos will not play and the app issues the error 'Cannot connect to Content Server'.  It's always the same videos that fail to play.

 

Help and advice appreciated.

Do these files have 6 channel sound?

Try selecting Direct Stream as the playback method, I have the same problem and this makes them play fine.