As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE FROM DCA TO BTV, THE CREW RECEIVED AN OPEN CABIN DOOR LIGHT. FLIGHT 4149 THEN DIVERTED TO PHL. WHILE ON APPROACH THE LIGHT CLEARED ITSELF. MAINTENANCE INSPECTED AND CLEANED THE DEBRIS THAT WAS FOUND ON THE SWITCH IN ACCORDANCE WITH DORNIER MAINTENANCE MANUAL 52-00-00. OPERATIONAL TESTS WERE PERFORMED AND THE AIRCRAFT THEN PROCEEDED ON TO BTV WITH NO FURTHER INCIDENTS.