namida_special shouldn't be accessible through the style manager in the first place (relevant pieces from it are instead included with the packs that use them), but this could mean there's a bug that causes it to (presumably, on a "if it was detected as missing, it gets put in the list even if it isn't on the downloadable list") - followed by NL thus trying to download a style that doesn't exist on the server, and getting a 404 error, which it then tries to interpret as a ZIP file because it hasn't been designed to handle such a situation.
So: There is a bug here, but not what you thought it was.
