Hello Trollitude, Were you using LTO4 media in your LTO6 drives?  If that is the case, then that is correct.  With LTO drives you can read & write one generation back & read only 2 generations back.     If you are using all LTO6 media then, you will want to use the L6 labels only so that the system doesn’t get confused & think that the media is LTO4.  If you are using LTO6 media, you can do an erase on the media & use the correct barcode & the media will be usable again.
We've had a TL4000 for years with two LTO6 drives and we've used some label sets ######L4 and ######L6 without any major problems. Two weeks ago, out of the blue, all tapes with labels ######L4 were marked as Gen4 and as read only. Can anyone tell me how to fix this or where can I find the label configuration to control this? Regards,
TL4000 marked Tapes as read only