Bacula or Drive problem?

Hi

I am using a Neo 24 Tape library with an LTO-9 drive.

The old one (Tandberg) broke recently and was replaced with a different 
one. Then the backups with Bacula worked fine for some time. Now I get 
those errors (again):

12-Jun 09:31 -dir JobId 1458: shell command: run BeforeJob "/usr/libexec/bacula/make_catalog_backup.pl MyCatalog"
12-Jun 09:31 -dir JobId 1458: BeforeJob: mysqldump: Deprecated program name. It will be removed in a future release, use '/usr/bin/mariadb-dump' instead
12-Jun 09:32 -dir JobId 1458: Start Backup JobId 1458, Job=BackupCatalog.2025-06-12_09.31.24_24
12-Jun 09:32 -dir JobId 1458: Using Device "LTO9-1" to write.
12-Jun 09:32 -sd JobId 1458: 3991 Bad autochanger "loaded? drive 0" command: ERR=Child exited with code 1.
Results=mtx: Request Sense: Long Report=yes
mtx: Request Sense: Valid Residual=no
mtx: Request Sense: Error Code=70 (Current)
mtx: Request Sense: Sense Key=Illegal Request
mtx: Request Sense: FileMark=no
mtx: Request Sense: EOM=no
mtx: Request Sense: ILI=no
mtx: Request Sense: Additional Sense Code = 20
mtx: Request Sense: Additional Sense Qualifier = 00
mtx: Request Sense: Field in Error = 00
mtx: Request Sense: BPV=no
mtx: Request Sense: Error in CDB=yes
mtx: Request Sense: SKSV=yes
mtx: Request Sense: Field Pointer = 00 00
READ ELEMENT STATUS Command Failed


No backup possible ("Fatal Error").

I do not know if this may be caused by Bacual or by the tape itself. Vendor says I must clean, however, the library is set to "autoclean" and a cleaning tape is available. I changed the cleaning tape to a new one, manually cleaned twice and tried again to backup with identical (errorous) result.

Any idea how to trace the problem to the tape or software? What to do?

Thank you.

Thorsten