As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT MAIN LANDING GEAR UNSAFE LIGHT REMAINED ON AFTER GEAR WAS RETRACTED. FLIGHT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. FOUND LEFT MAIN GEAR DOOR ROLLER OUT OF ADJUSTMENT. READJUSTED DOOR ROLLER ASSEMBLY, OPERATIONAL CHECK OK ON GEAR SWING. AIRCRAFT RETURNED TO SERVICE.