As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MIA - FLT 1574 - EN ROUTE ORD-SJU - CENTER HYDRAULIC QUANTITY WENT TO 0, THEN BACK TO 1.01, THEN 0, THEN BACK TO 1.01. LANDED IN MIA WITHOUT INCIDENT. VISUALLY INSPECTED CENTER HYDRAULIC QUANTITY. FLUID LEVEL READS FULL. CLEANED CANNON PLUG ON HYDRAULIC QUANTITY HYDRAULIC TRANSMITTER. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)