The machine wasn't writing properly or the tapes were defective or, more likely, someone just goofed up. The tapes weren't changed. Someone wasn't paying attention. Something went terribly wrong and now your data is gone.
Someone has to pay.
I t could be copy from an ad in a computer magazine or it could be your worst nightmare. Scenes like this don't play out every day, but they do happen. In five years, I have seen it happen twice in two different agencies. Luckily, in both cases, the problem was detected before data was irreparably lost. Making tape backups is a tedious and dull task.