I've reported this to Apple several times going back at least 3-4 months, but there's still a file-rename bug in iTunes 12.7.1 for users of iTunes Match and/or iTunes Music Library. If you remove the download for one or more songs in iTunes and then re-download, the file name of the first song re-downloaded is changed from the song's name to simply "download.m4a". (In a prior version of iTunes, the file's metadata would also get changed/overwritten — the little warning/error icon would appear in the iTunes list view and then the song's name would change to "download" — but Apple corrected that part of the bug a month or two ago. Now, the song's name no longer gets changed/overwritten but the file name still changes, which isn't as apparent since you need to Get Info to see it.) Maybe someone with a developer account can report this to Apple. Thanks.