As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - ON FLIGHT 2096, RETURNED TO FIELD, FO'S ALTIMETER FLAGGED OFF AND FD DADC MESSAGE WITH ADC INPUT FAIL MESSAGE FROM FMS. SAME SEQUENCE OCCURRED TWICE. MAINTENANCE REMOVED AND REPLACED THE NR 2 ADC. OPERATIONAL TEST GOOD. AIRCRAFT RETURNED TO SERVICE.