The RTBody object is a back-end class. Changes to the value of a back-end rich text object do not refresh in the UI.
When you call newrespUIDoc.Save you will overwrite the value you previously set with whatever appears in the UI (which in this case is blank).
Try using the UI Classes (FieldSetText or FieldAppendText) to set the value. You are already doing that for some of the other fields.
You can also check out this post from Andre Guilard -> http://www-10.lotus.com/ldd/nd6forum.nsf/0/dd507a5be7cc2e4285256eec005f56ef?OpenDocument