Cloudberry Desktop - 6.3.2.212

In the last couple of days, my file-based backup to a local storage in running so slow that it never completes - the admin panel reporting an estimated time to run of 9 years...

However, at the same time my Image-Based Backup to the same Local Storage is running as normal, so the problem is isolated to the File-Based backup and it suddenly started this behavior for no obvious reason.

The Local Storage device is an external HDD in a USB-3.1-G2 enclosure, connected to a USB-3.1-G2 PCI card, and I can do very fast transfers of large files to the device, so apparently not a hardware issue.

I have run chkdsk to make sure there are no issues with file corruption at the O/S level.

The only AV running is Windows Defender, and I've checked that no settings have changed, although the fact that image-based backups are working would suggest this not an issue.

Obviously, in these days where software vendors all do automatic updates, I can't rule anything out, but I'm not aware of any changes to the Windows-10 (19041.450) computer this is running on.

Where to start troubleshooting the problem?