UploadBug.php

<?php

//...

//Upload the new file
$upload = new Upload();
$upload->load($_FILES[$file['key']], "Form-Submissions/Form-One/{$sub->ID}");

//Retrieve the File Object
$newFile = $upload->getFile();

//We need to fetch the new file again otherwise things go wonky when we move the file...
/** @var File $newFileClass */
$newFileClass = get_class($newFile);

/** @var File $newFile */
$newFile = $newFileClass::get_by_id($newFileClass, $newFile->ID);

//Now we can move the new instance of the file
$newFile->setName($file['file'] . '.' . $newFile->getExtension());
$newFile->Title = $file['title'];
$newFile->write();