Comment 66 for bug 24234

Karmic. The same issue.

The problem is in intermediate proxy serveversm which caches file, that should not be cached. In my experiments, bug never-triggered on FTP. Bug disappear after removing transparent proxy. Bug disappear after disabling cache on transparent proxy.

Solution:
1. after the fail, try all known HTTP methods to force non-caching behaviour (Example of PHP header to fool caching proxy). Both for datafile and for signature!
        header('Expires: Mon, 26 Jul 1997 05:00:00 GMT'); // Date in the past
        header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT'); // always modified
        header('Cache-Control: no-cache, must-revalidate'); // HTTP/1.1
        header('Pragma: no-cache'); // HTTP/1.0
2. wait for wget fixes this bug: https://savannah.gnu.org/bugs/index.php?28137
3. Use FTP ot HTTPS protocols where available.