I have a whole bunch of partially found and lost episodes, I'll keep updating this comment.

for some reason this site is blocking me from editing so someone else can add them to the page.

https://archive.org/details/metallica-behind-the-music-extended-version/Metallica-Behind-The-Music-Extended-Version.mp4 This is the extended "remastered" metallica episode

https://archive.org/details/bad-company-behind-the-music this is the bad company episode, it is now Found.

https://archive.org/details/behind-the-music-the-day-the-music-died-fulllow-quality This is the "the day the music died" episode which is missing entirely from this page. There's two files. One is incomplete by about 13 minutes but it's better quality than the file that is the full version. I can't seem to find a better copy of the full episode.

https://archive.org/details/john-denver-behind-the-music_202304 This is the John Denver episode. No longer lost.

https://archive.org/details/blondie-behind-the-music-720p-encode This is the complete Blondie episode. It is now Found.