Change to the Save activity:

The 'To' property indicates the path of the file to be created. When not set, a file with a random name is created in the temp folder (either the folder specified by parameter TempDir of ServerConfig.xml configuration file, or the Windows temp folder if the TempDir parameter is not configured). What's new is that now, if the 'To' property is set to a filename (and not a complete path), then a file with the specified name is created in the temp folder.