A WhatsApp message with no order number is sitting in the box on my orders board. Can I remove it?

Yes. The box called WhatsApp messages we could not match shows one line per hidden name with all of its messages, six names per page. Type the order number, the booking number or the phone number and press Pair to match it, or press Clear to remove a line that belongs to nobody; it asks first. The Orders & delivery tab in the docs covers the box.