Bacula, Autochangers: insist on loading 'not in changer' media...

We have some setups using bacula (debian buster, 9.4.2-2+deb10u1) and RDX media, by the way of the 'vchanger' (Virtual Changer) script.

All works as expected, until the current mounted media exhaust the 'in changer' media (because exhausted it; or because simply users load the incorrect media...).

After that, bacula try to mount expired (purge them) or generically available volumes from other media, that are not in changer, putting them on error. We have extensively debugged vchanger script, that seems behave correctly.

Bacula seems have a current and correct state of 'in changer' volumes, and anyway a update volumes on console does not solve the trouble.

On director we have:

Autochanger {
        Name = SDPVE2RDX
        Address = sdpve2.sd.lnf.it
        SDPort = 9103
        Password = "unknown"
        Maximum Concurrent Jobs = 5
        Device = RDXAutochanger
        Media Type = RDX
}

Pool {
        Name = VEN-SD-SDPVE2RDXPool
        Pool Type = Backup
        Volume Use Duration = 1 days
        Maximum Volume Jobs = 1
        Recycle = yes
        AutoPrune = yes
        Action On Purge = Truncate
        Volume Retention = 20 days
}

On SD we have:

Autochanger {
  Name = RDXAutochanger
  Device = RDXStorage0
  Device = RDXStorage1
  Device = RDXStorage2
  Changer Command = "/usr/bin/vchanger %c %o %S %a %d"
  Changer Device = "/etc/vchanger/SDPVE2RDX.conf"
}
Device {
  Name = RDXStorage0
  Drive Index = 0
  Device Type = File
  Media Type = RDX
  RemovableMedia = no
  RandomAccess = yes
  Maximum Concurrent Jobs = 1
  Archive Device = "/var/spool/vchanger/SDPVE2RDX/0"
}

Device {
  Name = RDXStorage1
  Drive Index = 1
  Device Type = File
  Media Type = RDX
  RemovableMedia = no
  RandomAccess = yes
  Maximum Concurrent Jobs = 1
  Archive Device = "/var/spool/vchanger/SDPVE2RDX/1"
}

Device {
  Name = RDXStorage2
  Drive Index = 2
  Device Type = File
  Media Type = RDX
  RemovableMedia = no
  RandomAccess = yes
  Maximum Concurrent Jobs = 1
  Archive Device = "/var/spool/vchanger/SDPVE2RDX/2"
}

Thanks.