How is the movie named? Movies with numbers in the name can be difficult for Plex to correctly recognize. For such movies, be sure to add the release year in parenthesis. You can also add the imdb/tmdb ID to tell Plex exactly which movie to match.
Try this naming and perform the Plex Dance if necessary.
/movies <-- folder added to movie library
/The 33 (2015) {imdb-tt2006295}
/The 33 (2015) {imdb-tt2006295}.mkv
