As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WX RADAR PACKING UP FALSE RETURNS LT AND RT OF COURSE FOR ENTIRE FLIGHT @FL370/ FL390 AND IN DECENT MODE : AUTO AND MANUAL. GROUNDED - YES. PERFORMED WRX SYSTEM BITE CHECK REF B737-800 AMM 34-43 TASK 801 NO FAULTS FOUND. PERFORMED WRX SYSTEM - OPERATIONAL TEST REF AMM 34-43-00-710-802-001 NO DEFECTS NOTED.