there is one…
i replaced $file->download() with the following, and this seems to work fine.
// from here https://stackoverflow.com/questions/7263923/how-to-force-file-download-with-php
header('Content-Type: application/octet-stream');
header("Content-Transfer-Encoding: Binary");
header("Content-disposition: attachment; filename=\"" . basename($file->url()) . "\"");
readfile($file->url()); // do the double-download-dance (dirty but worky)