Sadly I've had the following conversation with a customer:

"I can't retrieve your data because it appears one of the tapes is too worn out to be read by the drive."

"What do you mean?! Our DLT-8000 tape backups are the best option, our previous IT vendor told us it's the best system in the business! It cost like $15,000 to put in place!"

"OK...sooooo...do you have any more backup tape sets I can try?"

"They're in the other room across the building."

*We proceed to walk by an area with one of the largest magnets I've ever seen in person.

"Do you put all your backups in this room?"

"Of course, it is secured..."

Long story short, I was unable to restore any of their data from those tapes even verifying with a brand new DLT drive.