Brake light issues

[andrewpclayton]

My neighbor is having issues with his brake lights, I am thinking its a ground issue or bad socket?

with the headlights off, brake lights work.

with the headlights on, the driver rear light is much brighter than the passenger side.
When the brake is pressed, the rear passenger lights all go out, and the driver side works very brightly.

82 c10

is this a ground? need a new socket? something else entirely that we havent yet considered?