i have the same issue ost awesome 1.16.3 has this bug, but osticket 1.16.3 does not and works as expected. when you attempt to download the zip with “Print/Thread+Internal Notes+Attachments” the .zip is corrupt. If you open the resulting .zip file in notepad, it seems to actually be a pdf file.
EDIT: the issue also happens when using the original osticket inside the osticket awesome, but like i said a clean install of osticket 1.16.3 works properly.