A loose or faulty cable can lead to issues when copying data from external hard drives, resulting in Macrium Reflect error 9, also known as "read failed 23." This error typically occurs when there's a problem with the connection between your computer and the storage device. To fix this problem, start by checking the connection inside your computer and cleaning any dirt or debris. If the issue persists, try using a new cable to ensure a stable connection. Once the connection is secure, you can proceed with copying your data, but if problems persist, there are additional troubleshooting steps you can take.