Losing files while moving to external network drive

I have a rule set up to move certain files to an external drive on another computer on my home network. Occasionally, this seems to go badly wrong; the original file disappears, but the target isn't fully copied - it's greyed out, and only a fraction of the correct size, as if it's only partially copied. Even weeks later, if I try to delete this file it shows up as being in use (presumably by Hazel?).

I imagine that there's no hope of rescuing the files lost in this way - but how can I avoid this in future?

What file protocol are you using to share this external drive? Is this other computer also running OS X (and if so, what version) or something else? Are you doing a copy or move operation?

My guess is a faulty protocol implementation or hardware at the destination. I have had a similar reported case with a badly implemented NAS so I'd suspect something like that in your case. Also, if it's weeks later, and Hazel is still running its rules on that folder, Hazel shouldn't be the one keeping that file busy. This would point to an aborted file operation which didn't clean up after itself.

You should check Hazel's logs to see if there are any errors there when doing a move. Hopefully you can find an entry specific to a file that didn't get transferred over correctly. Also, I'd suggest contacting me via email (use the "Contact Support" button in the "Info" pane) so I can go into more detail with you if required.