Issue found on (cache 4.5.11) but tested on demopublic45 (4.5.12) with same result.
What happens: upload pdf file with 640kB size to dms and put it into page as "download link". If you try to download it from public instance in Safari file is downloaded only with 512kB size, and because it is pdf, it cant be opened. If you download file again file is fully downloaded and all is ok. When cache if flushed then there is same problem again....