As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON PUSHBACK NO PARKING BRAKE LIGHT OR EICAS MESSAGE. ACCUMULATOR PRESSURE DROPS IMMEDIATELY WHEN HYD TURNED OFF. FOUND PARKING BRAKE SHUTOFF VALVE PARTIALLY OPEN. CYCLED MANUALLY AND IT OPS NORMAL. CYCLED PARKING BRAKE GOT ALL MSGS AND LIGHTS. NO HYD LOSS ON BRAKE PRESS.