As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAH - FLT 3939 - PILOT REPORTED THAT THE LT MAIN GEAR WOULD NOT RETRACT. THE AIRCRAFT RETURNED TO THE FIELD WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE LT GEAR UPLOCK, THE GEAR SYSTEM OPERATIONALLY CHECKED GOOD AND WAS RETURNED TO SERVICE. (X)