... As well as this ticket which says the issue should have been fixed 8 years ago: https://dev.deluge-torrent.org/ticket/1032 Is there something I can change in my setup to get this missing file > error state (not redownload) functionality? Thanks so much in advance ...

Search first... See ticket #1032

Will be fixed for next release: http://dev.deluge-torrent.org/ticket/1032

No the downloading of the file again has wiped out the original file... http://dev.deluge-torrent.org/ticket/1032

Are you sure the paths are identical? Have you set the actual drive or the symbolic link for the torrents to be moved on completion?

There is a known issue with unmounted external drives when Deluge starts up: http://dev.deluge-torrent.org/ticket/1032

It is usually only a problem when starting Deluge again. So you can modify the service or deluged startup routine to verify the mount exists.

There is a bug ticket for this issue: http://dev.deluge-torrent.org/ticket/1032

You need to move/remove the torrents from Deluge.

http://dev.deluge-torrent.org/ticket/1032

Keep an eye on http://dev.deluge-torrent.org/ticket/1032