Some local files not playing on iPhone or Mac Desktop, and are duplicated

[kaludiasays]

I've been using the local files function for a while, and had several songs synced on both my iPhone and Mac desktop. I added some more, and thought I followed the same process, but they didn't work right - if I played the file on my computer, I couldn't switch devices seamlessly to my phone like I could with other local files, and vice versa. The song files are downloaded locally on both devices (in Apple Music). Through turning things on and off a few times and downloading and redownloading, I was able to get all the songs except 1 to work. And even then, that song, plus another one, are duplicated in "local files" on mobile. How do I get the sync to work right like the other songs?