This issue could be caused by a corrupted driver, or one corrupt file. It is possible that the problem is with Windows i.e. Updates or reinstallations are required. Anti-rootkits should also be disabled.
Welcome to the Webroot Community. It will take many hours to scan your external drive. Go to the settings and disable scan mounted drives. WSA can take very long to scan due to this feature. www.webroot.com/safe
