On line 657 you have:
<form action="forms_application.php" method="post" enctype="multipart/form-data">
I think it will work if you update that to:
<form action="" method="post" enctype="multipart/form-data">
A blank form action will automatically use your current url including the url parameters, which would be necessary to make your update work properly. Currently your form submit isn't even going to the page where your update code resides.