If you have the correct dual contact bulb the outer part of the bulb does not come in contact with either end of the filiment, so grounding the housing is irrelevant.
Just like the map light and the dome light.
They all have constant power but only are illuminated when the door switch or dimmer switch makes contact to ground.
I think either... You have the wrong bulb, the wrong socket, or something is shorting inside the socket.