The controller will report an error, even if the area of the source drive that had the error did not contain data. Scheduling regular verifies will lessen the chance of getting this error.
You can force the rebuild to continue by setting the Overwrite ECC Error policy through 3DM 2, 3BM, or CLI, and then rebuilding the unit again. This will cause uncorrectable blocks to be rewritten, but the data may be incorrect. It is recommended that you execute a file system check when the rebuild completes.
Under Linux use
fsck /dev/sda1. If you have more than one SATA device, substitute the correct drive letter and partition number, such as sdb2, for sda1.