66 Coupe Crazy Taillight Issue

[Romerules2]

My left taillight has been having the following issues: Not very bright, the blinker/brake lights intermitently don't work, and when the tailights are on and I brake-the light just goes out. I replaced the taillight housing, the bulb, and the pigtail wiring connector. Now the light burns full force all the time it's on. I'm not much of an electrical genius, but I've had my wiring diagram out looking at it. Do you think my problem is in a) the light switch itself b) something in the wiring between the switch and the lights, or c) something completely different. It serves as the daily driver for my son going to school and back, so he's on the road every day with a car that's begging to get pulled over. Any ideas? I'm at a loss...Thanks.

[drchallenger-94sho]

bad ground