As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN POWER PUSHED UP TO TAKEOFF LEVEL, THE NR 3 ENGINE THRUST REVERSER UNLOCK LIGHT ILLUMINATED. AIRCRAFT RETURNED TO THE GATE AND MAINTENANCE DEFERRED NR 3 THRUST REVERSER PER MEL 78-1A. SPECIFIC PART CAUSING PROBLEM TO BE DETERMINED.