What will happen if we change the media type of existing media. For some reasons, we have a mixture of LTO5 and LT06 tapes in our environment.we have upgraded our tape drives from LTO-5 to LTO-6
In order to be able to read those LTO5 tapes (which have infinity retention) we had to make our LTO-6 drives as hcart2 instead of hcart3.
What you have done is the easiest.
I have always recommended to change drive density to match density of existing media.
Rather change density of a small number of tape drives, than having to change density of 100's of tapes (media).
You may have noticed that the user in the 2016 post stopped responding to attempts to assist.
So, no idea why it did not work for him to change density of expired media.