Dear all.
I found out a trick on my autochanger.
For this I used the Tandberg Web functionality Tools->Move Media.
As source address I entered the address of the drive (in my case Element ID 81)
and as destination address I entered slot 9 (in my case Element ID 9). That works fine.
Than I ran a re-inventory on the autochanger.
Last but not least I started bacula again, started update slots in bconsole and ran a label barcodes again.
The problem is solved.
br Robert