As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
F/O'S MCDU DISPLAYS AND FUNCTIONS NORMALLY FOR ABOUT 25 TO 30 SECONDS. THE DISPLAY THEN GOES BLANK FOR ABOUT 5 SECONDS WITH EXEC LIGHT ILLUMINATED AND CALL, FAIL, MSG, AND AFST ANNUNCIATORS ALSO ILLUMINATED. THE DISPLAYS THEN SHOWS A BIT PASS MESSAGE FOR ABOUT 5 SECONDS AND THEN MCDU OPERATES NORMALLY AGAIN. SEQUENCE REPEATS OVER AND OVER. ACFT GROUNDED. R & R MCDU, REF AMM 34-61-01, OPS CHECK OK.