From your posts: "during the restore, it selects the 3 other tapes correctly, but it does not
complete the restore, because of the 4th tape."
I suppose you are saying that Bacula restores the files in the others 3 volumes and then fails the job just in this last tape. If this is correct, you should have the files in the first 3 volumes in the restore directory even if the restore job fails on error because of the fourth tape.
Also, you can use bextract to restore files in the other 3 volumes, even if you delete them from your catalog.
This way, you can relabel this tape and try to reuse it (if it is not fisically damaged).
Regards,
Ana