This bug appears when viewing library via web app (Safari).
Summarised Library Structure:
[]Plex
[]Movies
[]Music
[]TV Shows
Under Movies
[]The Chronicles of Narnia_ Prince Caspian (2008)
[]Behind The Scenes
Inside Narnia
Sets of Narnia
... many other extra files
[]Deleted Scenes
Deleted Scenes
Bloopers
The Chronicles of Narnia_ Prince Caspian - 720p.m4v
The Chronicles of Narnia_ Prince Caspian - 1080p.m4v
Under this structure, none of the contents of the behind The Scenes to Deleted Scenes folders appear when the movie is selected in the Web App, only the Plex supplied trailer.
If the two main movie files are replaced with only a single file, and without the 720p or 1080p name attached (just the movie name), then all of both folder contents appear, as well as the Plex supplier trailer.
I think this might be a bug.
Cheers
Roger
PS, great product by the may.