Zero download size

Hi, after activating W3 Total Cache my downloads stopped working. I can download them, but only with zero size. I use WP-DownloadManager plugin and I found following headers:

header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");
header("Content-Disposition: attachment; filename=".basename($file_name).";");
header("Content-Transfer-Encoding: binary");
header("Content-Length: ".filesize($file_path.$file_name));
@readfile($file_path.$file_name);

It looks like Content-Length is somehow damaged by W3 Total Cache.

Related (not resolved) topic: https://www.ads-software.com/support/topic/plugin-w3-total-cache-download-script-fails-because-w3-total-cache-sends-its-own-content-length-header

When I disable all cache types, everything works well (no need to deactivate the whole cache plugin). But when I activate any of cache (Browser or Page or something else), problem with zero size is back.

Thank you for your help.