Self loading,
you are quite right in that permanent echos ie ground based objects should not show unless you wish them too....however I recall working Wallesy sector (Pole Hill) one day ,when we got horrendous ghost images and were giving aircraft avoiding actions on themselves....When engineers went to the radar station they found the bosses son inside the compound parked next to the radar head making out with his girlfriend!....the metal of the car was reflecting energy into the radar head and throwing the time scope out of sync hence two returns!