As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WEATHER RADAR IN AUTO MODE, THE FO'S SIDE DOES NOT FILTER OUT GROUND CLUTTER AT ALTITUDE. SETTING IN AUTO, WX + T, -2A @ FL380. GROUNDED - YES. PERFORMED B737-900 FIM 34-43 TASK 801, WXR SYSTEM BITE GOOD. REF B737-900 AMM 34-43-00 WXR SYSTEM-OPERATIONAL TEST-ANTENNA TILT TEST GOOD. GROUND VERIFICATION TEST GOOD.