As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB, MAIN CABIN DOOR RED CAS MESSAGE ILLUMINATED. CREW COULD NOT ADEQUATELY CONFIRM UPPER LEFT BAYONET POSITION. CHECKLIST FOLLOWED, EMERGENCY DECLARED, AND UNEVENTFUL LANDING PERFORMED. MAINTENANCE EVALUATION FOUND UPPER LEFT DOOR INDICATION MICROSWITCH INOPERATIVE. MICROSWITCH P/N 1159F50140-61 WAS REPLACED. PERFORMED SYSTEM OPERATION CHECKS AND VERIFICATION OF BAYONET INDICATORS, SYSTEM OPS CHECK GOOD.