As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI INTO POSITION FOR TAKEOFF, BRAKES LOCKED UP & RTO LIGHT ILLUMINATED. AIRCRAFT WOULD NOT MOVE. TOWED AIRCRAFT BACK TO GATE. REMOVED AND REPLACED ANTI-SKID CONTROL UNIT AND PARKING BRAKE VALVE PER MM. C/W BITE CHECK AND SPEED BRAKE RTO TEST PER MM, OPS CHECK GOOD.