On the download ftp file object in Automation manager, if the result isn't 0, the ResultString stays empty. If you look into the logs, you have the error next to the name of te object.
That is the whole point of having a ResultString output, to output the error message into this.
I'm guessing this is by far the only object in Automation Manager that has this flaw.
I would like to output this error to nCentral, but I do not have anyway to capture the actual error