As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RADAR IN AUTO MODE IS DISPLAYING RED RETURNS. WHAT WE BELIEVE IS THE GROUND OFF TO THE RIGHT SIDE OF THE AIRCRAFT. ALSO SEEMS TO OCCUR ODD. NOW RETURNS ON THE LEFT SIDE OF DISPLAY. NO ACTUAL WX IN THE AREA. GROUNDED - YES. ACCOMPLISHED WEATHER RADAR BITE PROCEDURE PER B737-800 FIM 34-43 TASK 801. WEATHER RADAR SYSTEM GOOD.