As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT, THE CREW RECEIVED A DAU NR 2 FAIL CAS MESSAGE. THE CREW CONTACTED MAINTENANCE CONTROL WHO INSTRUCTED THE THE CREW TO RETURN TO PIT. FLIGHT 4136 RETURNED TO PIT WITH NO FURTHER INCIDENTS. MAINTENANCE INSPECTED AND REPLACED THE NR 2 DAU IN ACCORDANCE WITH DORNIER MAINTENANCE MANUAL 31-00-00. OPERATIONAL CHECKS WERE PERFORMED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.