As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 4242 - DURING CLIMB-OUT FROM ATL-BTR, THE CREW RECEIVED A LEFT THRUST REVERSER UNLOCK MESSAGE ON EICAS AT APPROXIMATELY 18,000 FEET. THE QRH WAS COMPLIED WITH AND AN EMERGENCY WAS DECLARED. THE AIRCRAFT RETURNED TO ATL AND LANDED SAFELY. MAINTENANCE CLEANED AND ADJUSTED THE LEFT ENGINE THRUST REVERSER STOW SWITCH. OPS CHECKS GOOD. AIRCRAFT OK FOR SERVICE. (M)