As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NR 1 ENG REV UNLOCK LIGHT ON EICAS DISPLAYED ON TAKE OFF ROLL. THE INITAL PROBLEM WAS AN ACTUATOR LEAK. PDX RPL THE ACTUATOR. THE DEPLOY PROXIMITY SENSOR NEEDS TO BE REMOVED FROM THE OFF ACTUATOR AND REINSTALLED TO THE NEW ACTUATOR BECAUSE ITS HARDWIRED TO THE REVERSER. DURING THIS REINSTALLATION THE MECHANIC MUST OF MIS RIGGED IT OR LEFT THE SENSOR LOOSE BECAUSE THE VERY NEXT FLIGHT WAS THIS INCIDENCE OF THE UNLOCK LIGHT AND THE SENSOR WAS FOUND OUT OF RIG.