As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW RECEIVED A LEFT HAND OIL PRESSURE CAS MESSAGE IN THE AMBER RANGE AND CALLED MAINTENANCE CONTROL. FLIGHT 4056 WAS THEN INSTRUCTED TO RETURN TO CAK. MAINTENANCE INSPECTED AND REMOVED A OIL PRESSURE REGULATOR SHIM IN ACCORDANCE WITH DORNIER MAINTENANCE MANUAL 79-00-00. OPERATIONAL CHECKS WERE PERFORMED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.