So I just noticed that one of my movies in Plex would not play, with the error message:

Please check that the file exists and the necessary drive is mounted

Looking in Krusader, the file is definitely there. Checking each drive individually on unRAID, it seems like drives 1, 4, and 8 each have a folder for this movie, but only drive 4 actually contains the movie. Is this the cause? And if so, what's the fix?

Other movies seem to also have empty folders on a couple of drives, but they play fine.

This has happened with 3 movies to my knowledge, all of which Radarr had decided to re-download in the last two days despite having met the cutoff for quality, and therefore having no reason to download.

There's clearly something going on, but I can't wrap my head around what it is.