I'd suggest cloning it in the first instance (I normally use dd on a linux livecd but you should be able to do it in Mac OS https://www.cyberciti.biz/faq/how-to-create-disk-image-on-mac-os-x-with-dd-command/ )
After that mount the image and work on that rather than trying to use the failing drive.
Left CCC overnight to try copy the drive and it did it’s job. End up losing 26 files however i’ve Checked and they aren’t important so bullet dodged
@haveo started
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I'd suggest cloning it in the first instance (I normally use dd on a linux livecd but you should be able to do it in Mac OS https://www.cyberciti.biz/faq/how-to-create-disk-image-on-mac-os-x-with-dd-command/ )
After that mount the image and work on that rather than trying to use the failing drive.