What was found
DFW - FLT 1412 - AFTER TAKEOFF CRP WITH LANDING GEAR RETRACTED, LT MLG DOOR LOCK LIGHT ILLUMINATED. NO OTHER ABNORMAL INDICATIONS & ACFT PROCEEDED TO DFW, LANDING WITHOUT INCIDENT. BITE CHECK OF LANDING GEAR PROXIMITY UNIT WITH NO DEFECTS FOUND. ACFT DEPARTED DFW AS T1412/21 & AFTER TAKEOFF WITH LANDING GEAR RETRACTED, LT MLG WARNING LIGHT ILLUMINATED. ABNORMAL PROCEDURES CHK LIST & MASTER CAUTION PROCEDURE WITH SAME RESULTS. ACFT RETURNED TO DFW & LANDED WITHOUT INCIDENT. GROUND CHK REVEALED LT MLG DOOR BUMPER STOP BACKED OFF. REPLACED WORN LOCKING PIN & ADJUSTED LT MLG DOOR BUMPER. LANDING GEAR RETRACTION CHK WITH NO DEFECTS FOUND. FUNCTIONAL CHK FLT, NO DEFECTS FND. SYS OPER CHK NORM. (X)