Back up disk said to have corrupt parts

Did you elect to "repair" it?

If DU cannot repair it, reformat the disk. Often, they can continue to be used, and often for many years. When the errors become intolerably frequent, throw it away.

Goes without saying, don't rely upon one and only one backup device. "Two is one and one is none."

Just so you are aware, in macOS Sequoia (and earlier versions too), Disk Utility's First Aid primarily verifies and repairs the file system metadata, not the physical disk surface. On APFS volumes, that means checking the container structure, snapshots, volume roles, and directory trees. On HFS+ volumes, it runs through catalog files, extent files, allocation files, and similar metadata structures. Essentially, it ensures that the logical map of where files are stored is consistent and correct.

What it does not do is a true “surface scan” of the drive — i.e., sector-by-sector testing of magnetic platters on an HDD. First Aid assumes the underlying hardware is sound, and it doesn’t proactively scan for or remap bad block.

If you want a “surface test,” you’d need a low-level tool like DriveDx or the manufacturer’s diagnostic software.

Longshanks442 wrote:

I bought another external hard drive, dragged the files from the first drive over and reformatted the damaged drive. This error I asked about is appearing on the new drive.

If this is a Time Machine backup drive, then erase that new drive & start a clean TM backup. It is no longer possible to copy or modify files on a TM backup drive....any attempts will corrupt the backup.

Some other third party backup software may also not allow copying/cloning of a backup. Check with the third party backup software documentation.

Unless there is some sort of corruption with the files themselves, copying files to another drive should not cause any file system errors on the 2nd drive. If there are issues, then I would suspect a hardware issue of some sort. Perhaps with the computer, the USB-C Cable, or any other externally connected devices could be causing interference issues.

I’ll usually preemptively replace any hard disk drive reporting corruptions, even if the repair claims to resolve the issue.

DriveDx might provide some insight, particularly if the drive is reporting piles of errors.

I might continue using the questionably-reliable hard disk drive in parallel with its replacement, but I wouldn’t trust it again without stable operations for a few months, and not without some heavy I/O loading such as from a complete read or complete write.

Longshanks442 wrote:

I believe there is some corrupt files that cause this message to appear. The drive has nearly 8T of data on it. These are mostly very large fine art photographs and all the source materials for the final images.

This is a backup? Why not just get another new drive and create a new backup from the source?

After running Disk Utility, a corrupt volume is listed, but the last message from DU is "Done". Might that indicate I don't need to worry about the corrupt volume?

The First Aid summary will lie. Click "Show Details" & scroll back through the report to see if any unfixed errors are listed.

What type of backup is this? What software was used?

As I understand it, Disk Utility is reporting errors that cannot be fixed on a new external hard disk drive. If that is correct then return the new hard disk drive for a refund.