[embed form] issue with upload field / version 4.0.1

@EJL @joeyk
I have created a test link with the form. If you fill out the details and try either a PDF or JPG you will see the form does not work.
https://code.devscreen.com/4sight/m.php

We get some issue with server error, see console. But this still does not make any sense as there is a cross origin issue. We have tested this on a different server which does not have cpanel but vanilla setup. So we are trying to isolate the issue here.

If you could take a look that would be awesome
thanks
M.