What was found
AIRCRAFT RETURNED BACK/FLIGHT (LSZH - LGIR) DUE TO AT CLIMB STATE, PASSING FL 230, THE CABIN DOOR CAS MSG (STEADY) APPEARED. THE AIRCRAFT LANDED SAFELY BACK TO LSZH. ON GROUND, CONTRACTED MAINTENANCE PERFORMED TROUBLESHOOTING AND FOUND CABIN DOOR UPPER AFT PROXIMITY SWITCH WITH 2MM DISTANCE AFAR THE TARGET. MAINTENANCE ADJUSTED THE CABIN DOOR UPPER AFT PROXIMITY SWITCH IAW AMM 52-70-00, OPERATIONAL CHECK, DOOR OPERATION AND INDICATION NORMAL. AIRCRAFT PRESSURIZATION PERFORMED WAS SATISFACTORY.