As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN IN FULL BRIGHT, FIRST OFFICERS MCDU SCREEN FLASHES ABOUT ONE PER SECOND. GROUNDED - YES. CHECKED AND COULD NOT DUPLICATE INTENSITY OR FLASHING ISSUE. AS A PRECAUTION REMOVED AND REPLACED FO'S MCDU PER B737-900 AMM 34-61-01. INSTALLATION TEST SUCCESSFUL.