As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
STL - FLT 29 - AFTER TAKEOFF WHEN LANDING GEAR WAS RETRACTED, LANDING GEAR UNSAFE LIGHT REMAINED ILLUMINATED. CYCLED LANDING GEAR. FOUND LEFT MAIN LANDING GEAR PROXIMITY SENSOR. LANDING GEAR INDICATION AND OPERATION THEN CHECKED NORMAL. (M)