confounding brake lights on 220S

[DavidF]

The brake lights on my 1963 220S haven't worked reliably since I started working on the car two years ago. Some times one will work, but not the other, unless I bang on the light panel with a fist.
I cleaned it with steal wool and coated it with dielectric grease. All the other lights in the panel work.
I got a new switch two weeks ago and the lights appeared to be working. I then replaced the brake booster. Now the lights are not working.
Banging on the panel doesn't work anymore and I tried to clean the switch by depressing the spring. No go.
Any guesses?
Thanks,
David

[Marrs]

I had this and after cleaning the bulb holder, contacts etc., I realized the ground wire was not contacting properly and had to clean it and it's mating surface very well. Often you can tell it's the ground if while the light is not functioning as it should if you touch the chrome bezel and touch the bumper or other metal it will usually light up until you then remove your hand. You are acting as the ground in this case. Good luck!