I remember one time I fat-fingered a tag like this:
Something, Something-Behindthescenes.mkv <—case sensitive
and it killed every extra in the folder.
Also, if you have versions of movies in different resolutions (for instance), ya gotta do this:
Extras that appear, then disappear rings a loud bell - 'cause that’s exactly what happens…
If either of those two things don’t apply - disregard.