What does "Update Attachment" mean? What does it update? I can't figure it out, it is next to "Add Attachment", so it is not updating previous attachemnt.
IIRC, if you select a file with the same name as an attachment that already exists, it'll replace it.
If it is the case, it should be near old attachment, not next to new one. I think no user understand it, it is just strange button. I'll just remove it in template, you can always delete attachment and reupload new one if you want "updating".