As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CAPTAINS RADAR DISPLAY ON NAVIGATION DU SHOWS CONSTANT RETURN AT 10'O CLOCK, 2'O CLOCK POSITION, 5NM RANGE. VARIES WITH MODE/GAIN/ANTENNA ANGLE ADJUSTMENTS BUT ALWAYS PRESENT. DOES NOT APPEAR ON FO'S SIDE. GROUNDED - YES. CW WXR SYSTEM TEST REFB737-800 AMM 34-43-00 OP CK GOOD NO UNUSUAL RETURNS NOTED.