Using S3 as my CDN.
When uploading images through the media page example.com/wp-admin/upload.php I don't have any problems. However, when I try to upload media through the modal which opens when editing a page ("Add Media" button, "Upload Files" tab) I get an error "The uploaded file could not be moved to ..."
Obviously the file permissions are correct, or I wouldn't be able to upload from the Media page. Any idea why it only fails when uploading through the modal?