Eventhough the required field is selected like suggested:
[dropuploader* dropuploader limit:5000000 count:5 filetypes:jpg|jpeg|pdf|gif|png]
The field seems to be not mandatory and the form can be transmitted also with no images.
Thanks in advance,
I copied your form to my site and seems it works right (Drop Uploader field is required) but on your site I can send form without files.
Can you tell me – do you use some custom plugins for Contact Form 7?