Typically due to using the option to "Verify File Copy" in the Secure Copy | Performance tab.
The "Verify File Copy" option causes a CRC (Cyclic Redundancy Check) checksum to be performed on each completed data packet in the copy job. This option is useful in unreliable network connections such as dial up links or satellite connections. However, if any utilities such as Anti-virus or Data Deduplication are in use on either the Source or Target volumes, the checksum will fail. The files may have to be repeatedly re-copied.
If the copy job is being performed across a reliable network connection, disable the option to "Verify File Copy" option.
