Remove the spaces before and after the hyphen.
But: you’ll be much happier if you combine the two parts immediately after ripping them: [HowTo]: joining multi-part movies files with MKVtoolnix GUI
That way you can avoid all of the weird things which don’t work with multi-part videos.
Consider naming the combined movie as
Gettysburg (1993) - {tmdb-10655}.mkv, particularly if you already have a video with a similar title in this library.
That is embedded into the mp4 file as meta tag. Either prevent it from getting into there in the first place, or remove it using a metadata editor like e.g. mp3tag
This folder name is not recognized in Plex.
See https://support.plex.tv/articles/local-files-for-trailers-and-extras/ for instructions on how to add bonus material.
After preparing the files as described above, you are best off performing a full Plex Dance with the movie and all its extras.
Disable automatic library updates - or -
Never rip/download directly into a folder which has been added to a Plex library.
Otherwise there is the danger of Plex trying to match a file which is still in the process of being copied/ripped/downloaded. Which can easily lead to wrong matches.
