Just out of interest, I "believe" (take everything with a pinch of salt) that VLC crashes because of embedded sub titles in the mkv (and sometimes MP4) files.
I use another video player now which has no probs of this kind.
I had a recent version of VLC installed on my Win7 and when I tried to play a particular mkv file I got an error message saying there had been an undefined fault and I couldn't do anything about it. So, I upgraded to the latest version of VLC (2.2.1) and matters went worse. VLC flashes on the screen...