I don’t know if this is the exact same thing, but I am also having huge difficulties getting a 600GB backup to Amazon to complete. It fails at least once a day. I suppose it’s a problem with Amazon. However, my gripe with duplicati is that whatever amazon does or does wrong, it should be able to handle it in a meaningful way. Currently, what happens for me is that it just stops uploading. No error message, nothing. The progress bar just stays where it was and nothing happens.