通过PHP下载对某些用户不起作用

Question

To download the file I'm using the GET request to the download server like domain.com/?file=/uploads/files/03/48/51/2017/04/09/file.rar

On my computer, like most users, the download goes well. But for some users (about 10-20% of total), there are errors. From their words (different users):

1. In Chrome in download status Network Error: Network Error
2. 502 bad gateway
3. Download file as php.
4. Antivirus block.

5. 404 error

           function clean($string) {
             // $string = str_replace(' ', '-', $string); // Replaces all spaces with hyphens.
              //$string = preg_replace('/[^A-Za-z0-9\-\.\_]/', '', $string); // Removes special chars.
   
              return preg_replace('/\.\./', '', $string); // Replaces multiple hyphens with single one.
           }
   
           function file_force_download($file) {
             $file = clean($file);
             if (file_exists($file)) {
               if (ob_get_level()) {
                 ob_end_clean();
               }
               if ($mimetype = mime_content_type($file)) {} else $mimetype="application/octet-stream";
               header('Content-Description: File Transfer');
               header('Content-Type:.'.$mimetype);
               header('Content-Disposition: attachment; filename=' . basename($file));
               header('Content-Transfer-Encoding: binary');
               header('Expires: 0');
               header('Cache-Control: must-revalidate');
               header('Pragma: public');
               header('Content-Length: ' . filesize($file));
   
               if ($fd = fopen($file, 'rb')) {
                 while (!feof($fd)) {
                   print fread($fd, 1024);
                 }
                 fclose($fd);
               }
               exit("Error while reading file");
             } exit("File does not exist");
           }
   
   
           $file = $_GET['file'];
           $file = preg_replace('/uploads\/files\//', '', $file);
           if (preg_match("/\d\d\/\d\d\/\d\d\/\d\d\d\d\/\d\d\/\d\d\/.{1,60}/i", $file)) {
   
            file_force_download("uploads/files/".$file);
           } else exit ("Incorrect file link");
   
       ?>
   

I tried changing the download server and the domain does not help. Why this happens?