As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) AT CRUISE ALTITUDE OF 23,000, THE LT REV UNLOCKED CAUTION MESSAGE APPEARED WITH THE REV ICON ON THE N1 GAUGE AND THE T/R REV EMERGENCY STOW LIGHT ILLUMINATED. EMERGENCY DECLARED. THE MAINTENANCE REPLACED THE THRUST REVERSER / PDU FLEXSHAFT LOCK OUT UNIT. AIRCRAFT RETURNED TO SERVICE.