Symptoms

Backup fails with this error:
Failed to enumerate directory. It may be corrupted or does not exist. Check the disk for errors.

Cause

Issue in the product. A folder which name ends with a space is selected for the backup.

Solution

Acronis True Image Subscription:
The issue has been fixed in build 6106 (Acronis True Image New Generation). Please update to the latest build.

Acronis True Image 1-Time Purchase License:
The issue has been fixed in the next update. This article will be updated as soon is the new build is released.

As workaround, you can rename the folder and delete the blank space at the end of the folder's name.