Unable to repair bad sectors

I am trying to repair my drive using the extended test in DLDIAG.
However it’s not working. I get an error message stating Unable to repair bad sectors and that I should contact WD technical support.
The internal drive is used in a Synology NAS along with another drive that has the same problem.
I have connected the drive vai a USB/SATA cable.
The drive is not available from Explorer so I cannot take further backups.
Suggestion ?

A NAS uses a completely different formatting method from what a PC uses. This is why it’s not available on the PC.

I’m no expert but it sounds like you need to replace those drives.

Thank’s for the reply.
Originally I got the problem while the drives were within the NAS.
I ran the tests after connecting the drives directly to my computer via the USB/SATA cable.
The quick test is OK.
The repair in the extended test does not work.
It’s weird that I got the same problem on both drives at the same time.
I have contacted Synology as well…