In version 6.40 I noticed that my fill server was always downloading. If I disabled it then the main server was able to download all of the parts. I checked in the server tab and it shows my fill server as a fill and slave. I tried 6.41RC1 and still have the same issue. I've tried restarting newsbin with both enabled and it produces the same result. Both are configured to use SSL if that makes a difference.
I see no errors in the logging tab. Is there anything to try?