Reckordbox won't erase music files from USB

Hello, I'm an Italian professional DJ using the last version of REKORDBOX 2.0.2 (with CDJ 2000, last  firmware)

I noticed that sometimes (not always)  when I erase a song from the USB  SDHC card or stick, (of course not from the play-list but selecting "ALL TRACKS"  from media), the song is deleted from database, but not from the media, if I search it again from "ALL TRACKS" (on media through Rekordbox ) i cannot see the song any-more, but if I search the file into the folder "CONTENTS" on the media

the file is still there; so I must erase it manually.. Now I'm trying to guess how many songs that I erased from "all tracks" are still on the media, before I discovered this problem

 Not only a problem of space on the media, but also a legal problem here in Italy, because we have  a special license, to legalize the files we use to perform, and as I erase songs from media I expel  them from license too; so if they will check my media they could find songs that I could not use anymore.

I tried to investigate why this happens, first I was thinking that the problem was the "flag" "read only" on the "M4A" files imported from iTunes, but also removing the "read-only flag" the file was not deleted from media.

And now I discovered that also some normal Mp3  files (320Kbs)  without  read-only flag in the file has not been deleted.

Any idea to solve this? Thanks