MythVideo: Failed to delete file

[fabio]

When I tried to delete file (e.g. spman-6_10.avi) from VideoGallery o VideoManager I get the an error: "Failed to delete file"

The files are stored in a slave HD.

mythtv user has the grants to delete the files:

-rw-rw-r-- 1 mythtv mythtv 759275520 dic 8 19:35 spman-6_10.avi
-rw-rw-r-- 1 mythtv mythtv 659617513 dic 8 20:54 spman-6-5.mkv
-rw-rw-r-- 1 mythtv mythtv 585041920 dic 8 18:44 spman-6_6.avi

user@mediacenter:# apt-cache policy mythtv
mythtv:
  Installed: 2:0.28.0+fixes.20161202.128e297-0ubuntu0mythbuntu3
  Candidate: 2:0.28.0+fixes.20161202.128e297-0ubuntu0mythbuntu3
  Version table:
 *** 2:0.28.0+fixes.20161202.128e297-0ubuntu0mythbuntu3 500
        500 http://ppa.launchpad.net/mythbuntu/0.28/ubuntu xenial/main amd64 Packages
        500 http://ppa.launchpad.net/mythbuntu/0.28/ubuntu xenial/main i386 Packages
        100 /var/lib/dpkg/status
     2:0.28.0+fixes.20160413.15cf421-0ubuntu2 500
        500 http://it.archive.ubuntu.com/ubuntu xenial/multiverse amd64 Packages
        500 http://it.archive.ubuntu.com/ubuntu xenial/multiverse i386 Packages