Dome light issues

1974 dodge. My dome light works perfectly if I remove the lens cover and unscrew the bulb assembly from the roof of the truck, but when it is screwed in (grounded) it stays on. The assembly has 2 wires, the door switches have 1 wire. The only bulb I have is a 2 filament bulb. Its not a huge deal but it would be cool if it worked correctly.

Any ideas are appreciated for sure. Thanks.