Some mkv files work, most are unable to playy

I have read some of the previous threads and haven’t seen an answer to my exact problem. Some mkv files play, but most do not. I have more than enough room on my hard drive for the files to play but some of the files still have trouble. Any help is appreciated.

Is this a problem only when transcoding is required? Then you need to ensure that your temporary transcoder location has sufficient free disk space.