whats wrong with my headlight

If the either headlihgt bulb is working at all the single factory ground attachment is obviously good. I dont think it will be nesessay to do a lot of re-engineering the electrical to repair a bad bulb.
On the other hand.. If you are installing modern bulbs that draw more current than the originals, you probably will end up re-engineering the headlights power supply. Much more than the chassis ground too.