Apple Music - Some sounds from Album are not available to download or listen
I'm not sure what the reason is behind this, or if it's a bug. But generally I've had this occur when I either previously owned that song or uploaded it, or if I downloaded that song as a single (I.e. Free single of the week, etc.).

Either way, removing the entire album and any duplicate versions of that song, and then re-adding the album usually fix it for me. Best of luck!