Hello
I am not using wizard, instead I use bprecover command from the command line. To be honest in NBU 6.5 there is a switch to this command -wizard :D.
Once You will reconfigure Your NBU catalog backup to disk and perform one backup You can try to run this command
bprecover -l -dpath disk_dirve:\Directory_with_NBU_DB_BACKUP to see if backup was successful.
I think that in wizard there is an option where to point out disk path for NBU DB