Diagnostic Test Full or Short: Self Test failed

I think i have some bad sectors in the HDD of MyBook live. But when i do Diagnostic Test (short or full) in the utilities menu, it ends up with: ‘self test failed’. How to solve this?

That’s a good indication that it’s a bad drive. If you don’t have a backup, and the drive is still accessible, I would get the data backed up asap. Otherwise, you may be looking at data recovery.