Not quite sure whats going on but I have movies that will not match properly even when I select the right movie, It shows double thumnails of the same movie, but only 1 i can edit. Here are examples of my rocky films. These are .mp4s, rather than most of my movies which are mkv… I’ve used filebot to properly name each folder and file.
mp4 files are notorious for containing embedded metadata. And these metadata are more often than not incorrect.
Your best course of action is to remove those metadata completely.
You can use Windows’ file explorer to do it or a special tagger software, like mp3tag.
Afterwards, perform the Plex Dance with those movies.