I found this text in the support incident:
I did some more checking and testing. In the file manipulation helperphp.php file around line 690 the header is set. I made the following changes before the line that reads the file from the system.
// set headers for download file
header("Pragma: public"); //added
header("Expires: 0"); //added
header("Cache-Control: must-revalidate, post-check=0, pre-check=0"); //added
header("Cache-Control: public"); //added
header("Content-Description: File Transfer"); //added
header('Content-Type: application/octet-stream'); //original line
header('Content-Disposition: attachment; filename="' . $fileName . '"'); //original line
header("Content-Transfer-Encoding: binary"); //added
header("Content-length: ".filesize($path)); // original line
does that work for you as well?