If you aren't careful, you can spend valuable time looking in the wrong place for a solution. Use the symptoms to access the situation, but realize the problem causes the symptom, it's not the symptom itself. Remember if a bulb doesn't work and is not burned out and the base shows damage, the fixture will also show the same damage inside the socket. Replacing a bulb will not fix a loose connection. The fixture or socket/lampholder must be replaced.