Page: https://www.greenpeace.org/international/wp-admin/upload.php

Description of the issue: "Unexpected response from the server. The file
may have been uploaded successfully. Check in the Media Library or reload
the page."

This bug was reported to me by a user w/ a Campaigner role.

I was not able to replicate the issue. I was able to upload their file
successfully. They "tried a few times" before reporting the bug to me.

Attachments:
https://drive.google.com/open?id=1Snb8TntXtscKrJ2ZWloHLBspAHnbCX_j