[schimi2k]

You can edit Mkv header with MkvToolNix header editor

Yes. I use toolnix to set the headers originally. I don't believe that the headers are the problem since they are set correctly. The problem is that language flags are only being displayed for about half my videos. I just don't know if this is a scraping problem and the headers are not being read or if it's a display problem.

after you "installed" the language addon, did you restart your whole player ? and maybe refresh your video db ?
and maybe start a movie without a flag and check if you have the flag after play it a cpl of seconds
and finaly check if you have activate:
SETTINGS >>> VIDEO >>> FILE LISTS >>> EXTRACT THUMBNAILS AND VIDEO INFORMATION

if those things wont work, send me a pm with one of your movie infos without a flag and one with a flag please