Managing barcodes

Did you create this barcode rule?

Please change it as per my post above so that the default will be Scratch and Media Type the same as the tape drives.
So, if your tape drives are LTO4 and the density is hcart2, the media type must be the same.

barcode tag:  <DEFAULT>
media type:   hcart2
pool name:    Scratch
Max mounts:    0 (no maximum)
description:  ---

Now - let us look at the vmcheckxxx output.

It shows 48 tapes in the robot - 12 tapes with barcodes and the rest with no barcodes.

Is this correct? Did you only stick barcodes on 12 tapes and the rest have no barcodes?

You should NOT be using barcoded and non-barcoded media in the same robot. 
Each time you run an Inventory, NBU will assume all non-barcoded media are new and add new A00 numbers.

Have you been using these non-barcoded tapes for backups up to now or are these tapes all new?
If tapes have been used before for backups, you need to tell us.
Adding barcodes to tapes with backups on them is going to create all sorts of issues (Frozen media) unless you 'marry' the previously used A000 media-id with the new 000... label. 
We will help you if this is the case.

One more thing - 
You can see in vmcheckxxx output that NBU uses the last 6 characters as media-id, meaning that it sees the L4 suffix as part of media id.
This is not ideal - best to use the 1st 6 characters as media id.
So, 000013L4 should be  Media Id 000013, not 0013L4.

To fix this, use the Media ID Generation tab to tell NBU to use the 1st 6 characters:
Robot number: 0
Barcode length: 8
Media ID generation rule: 1:2:3:4:5:6

So, in summary:

Run Media List Report (bpmedialist) to see which tapes contain backups.
Remove all non-barcoded media from the robot (if these tapes contain backups, you need to make a note of each tape's A000 number)
Delete existing tapes that were added as DTF_CLN media type.
Change Barcode Rule as per my suggestion above.
Add Media ID generation rule
Run Inventory.