Hello,
This happens in Windows 10 and Linux. For DVDs that are only part subtitled with automatic subtitles, the subtitles don't show.
E.g. Game of Thrones has world languages other than English (Valyrian, Dothraki) - and these languages aren't automatically subtitled when I play DVDs on my computer, whereas they are if I use my actual DVD player. The only way I can see the subtitles is if I set English subtitles on, but then everything is subtitled, including the English audio. Breaking Bad is another example - the automatic English subtitles for the Spanish that show up on regular DVD players, don't show up playing with VLC.