As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER APPLYING T/O, POWER AND BEGINNING TAKEOFF ROLL AT APPROX 10-20 KTS THE PARKING BRAKE TAKEOFF CONFIG WARNING ANNUNCIATED MID A/C FLT ATTENDANT STATED SHE FELT A CYCLING OF BRAKES AND SHUTTERING. LUBED PARKING BRAKE VALVE MECHANISM. RERACKED TAKEOFF CONFIG CARD M620 PERFORMED T/O CONFIG TEST ALL PASSED.