The "drive" IS the files. The files may be corrupt and, therefore, unreadable, or the disk may be defective, e.g., bad sectors, and therefore unreadable. Whatever the reason, not being able to properly read files creates issues.
Have you read the ckdsk log in EV?
Did you try to clear the dirty bit as PoorMan suggested?
Does the backup log specifiy the corrupt files. Obviously, if they are JPEGs of your dog, the SFC will not correct those.