I think from his post he is saying it keeps trying to redownload all 6GB.
If that is the case, then this is very unlikely to be occurring, unless something on your computer is removing the files during the process/before you've restarted the launcher perhaps.
Note that after you've closed the launcher it has to 'reread' the files. If the files have downloaded, then I think it still shows them as downloading, but will skip past them as it'll know they are already there. (I dunno, I've never actually had to download in chunks). Make sure you give it 5 minutes or so at the start of you relaunching the server to make sure that the files aren't actually be downloaded again.