If there are whitespace in the filename. You get a wrong download name in return.
Also the extension is removed!
Issue #8383 was marked as a duplicate of this issue.
cyrillyc character also corrupt filenames:
"ФУН. Набор дополнительных правил 1.pdf" will be downloaded as "$#-. -01-@ 4---"
This issue appears to have been fixed some time ago. Marking as resolved.