Filling out all required fields in the properties window (Partner Link, Operation ...) by typing into the corresponding text areas will not be noted by the BPEL editor. The user must use "Quick Pick" or "Content Assist", otherwise the data will not be saved.
IMO if the typed in "partner link" and "operaion" data is valid then the "quick pick" tree should be updated accordingly - or direct editing of these fields should be disabled.