Try removing the files from this library, then do another metadata update.
Afterwards put the files back to their designated place and refresh the metadata one more time.
If the files still don’t show, can you please share your server logs so we can take a look at what’s going on? File name length shouldn’t have an impact.
please provide your server logs (see description in the link; the console screenshot is too limited)
what agent are you using for this tv-show library? ⋮ > Manage Library > Edit... → Advanced > Agent
Some of the legacy agents had a dedicated setting to enable local extras; the Plex TV Series agent should automatically pick them up.
As those are all mp4 files… let’s verify there’s no conflicting embedded metadata – you can e.g. use “Subler” for that job… I’m particularly interested in the file’s embedded title. → With that I’m trying to rule out if your embedded title might give the impression this is a regular episode and mismatch/misplace it somewhere else.
Can you remove the leading # in the extra names (maybe start only with the interviews). This should not cause problems… however I’d like to rule out that there’s some kind of interference we have overlooked before.
After changing the file names for those extras, please re-re-re-re-refresh the metadata of the show once more.
I ask you one last information: is it possible to give an alphabetical order to the Extras?
As you can see from the last image there is a first Extra which is the Trailer and starts with the letter “S” (and it could be logical to have it as the first), followed by two “S6” which should be seen after “S2”, " S3 "and …
That’s a known bug. For all I know Plex have it on their agenda to return the extras in alphabetical order. As usual there’s no ETA of confirmation if/when this will happen.