As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FL 290, CENTER HYDRAULIC QUANTITY LIGHT CAME ON WITH DROP IN BRAKE PRESSURE. ALSO, HAD RESERVE BRAKES AND STEERING LIGHT COME ON AND OFF. THEN QTY INDICATION FLUCTUATIONS. DIVERTED JFK, LANDED WITHOUT INCIDENT. VERIFIED HYDRAULIC QTY FULL, REPLACED CENTER SYSTEM QTY TRANSMITTER. OPERATION NORMAL. ETOPS CATEGORY 'B': DIVERSION OR TURNBACK