As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON ARRIVAL AT GATE, YELLOW SYSTEM PRESSURE WENT TO ZERO, PARKING BRAKE SET PRESSURE BLED TO ZERO IN TWO SECONDS, GREEN SIDE OK. MAINTENANCE COULD NOT DUPLICATE PROBLEM, INSPECTED BRAKE AND HYDRAULIC SYSTEM NO LEAKAGE NOTED. PERFORMED CHECK IAW AMM ALL CHECKS GOOD.