As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: RETRUN TO FIELD, EMERGENCY DECLARED. ALL FOUR BRAKES APPEARED TO DRAG. BRAKE PRESSURE WAS JUST ABOVE 0. REQUIRED 39-41% N1 TO TAXI ACFT BACK TO GATE. BRAKE HOT ECAM. MAINTENANVE REPLACED #1 BRAKE SAFETY VALVE (2620GM) IAW AMM 32-43-16.