Flickering Lights

I know that this is not the problem you have, but many years ago, a friend had a single flickering courtesy light bulb. Voltage at the connector seemed fine and steady. We checked the bulb and it looked good...that is until I rotated the bulb between my fingers. The filament was actually broken at one end and the engine/car vibration made and un-made the connection, causing a flicker. I figured that all the arcing inside there would soon kill the filament. He changed the bulb.