> Once you complete the certification of Boeing Commercial Airplanes’ design enhancement for ensuring the complete closure of Boeing 737 mid exit door (MED) plugs following opening or removal, issue an airworthiness directive to require that all in-service MED plug-equipped airplanes be retrofitted with the design enhancement. (A-25-15)

It sounds like Boeing is currently working on designing and certifying a design enhancement to the MED plug to make it obvious if one is not closed properly. Not sure where to find the details on it though.