What was found
AIRCRAFT WAS GROUNDED: LEVEL CRUISE FL 390 ALL SYSTEMS NORMAL .OXYGEN PASSENGER AMBER MESSAGE ON ECAM,OXYGEN PASSENGER SYSTEM ON LIGHT ON OVERHEAD ON.PASSENGER O2 MASKS DEPLOYED IN CABIN. CABIN PRESSURE NORMAL.DOOR INDICATIONS ALL NORMAL. FL 390" CABIN WAS AT 8000 FT.. AS A PRECAUTION AIRCRAFT DESCENDED TO 25, 000 FEET AND THE AIRCRAFT DIVERTED BACK TO MIA. THE AIRCRAFT MAINTAINED NORMAL SCHEDULE ALL THE WAY IN DESCENT TO LANDING. AT MIA. NO EMERGENCY WAS DECLARED AND THE AIRCRAFT LANDED SAFELY WITHOUT FURTHER INCIDENT. **SUPPLEMENTAL REPORT FOR AALA202111123616: REPLACED ALTITUDE SWITCH AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 35-23-15 AND AMM 35*-23-00.** (CLOSED)