Unable to play some movie MKV files

[Sparrowlogins 18]

I have recently converted my iso files to mkv for movies.  I am having trouble playing some movie files using the web client, especially the HD ones.  They begin play but the player closes and I am back at the info screen.  occasionally I receive an error message. 

 

For some films, lowering the resolution helps, but not all.  I have a 152mb download and 15mb upload, so should be able to stream the films at HD quality.  I have checked my firewall settings and there is no traffic shaping or priority management enabled and the port is open as it should be. 

 

I seem to be able to play TV episodes ok, but perhaps as these are mostly 720 or 480?

 

I cant seem to get a screenshot either - the error is too quick.

 

Anyone else had this issue or know where I am going wrong?  Perhaps my transcoding settings are wrong ( they are set up to auto decide currently )

[Koleckai Silvestri 1154]

What browser are you using?

[Deathsquirrel 745]

Do the movies play in a browser when on your local network or actually on the server?  Your description makes it sound like you're having trouble when streaming from outside your network.

[Sparrowlogins 18]

This is outside my network using IE10 and IE11