Got a funky electrical gremlin living in the rear passenger brake light housing.

Scenario 1. Parking and or head lights switched ON and depress the brake.
The rear passenger side parking light goes OUT and brake light will NOT illuminate. So, press the brake pedal and all lights in the rear passenger side housing go out.

Scenario 2. Parking and or head lights switched OFF and depress the brake.
The rear passenger brake light illuminates normally.

Scenario 3. Keep foot on brake pedal switch on parking or head lights rear passenger side lights go out. Foot off brake, the lights come on. Foot on brake, they go out.....

I switched the drivers side bulb with the passenger side bulb, but the problem persisted.

 

Water in the rear light cluster? Drilled mine.

 

Someone already beat me to it. There are three ~1/4" precisely drilled weeping holes running along the bottom of the lens. No water is sitting the housing at the moment.

 

Bad ground or contaminated socket?? check both sides.

 

The grounding contact in the housing was not making proper contact w/ the bulb. I squeezed it to form a tighter bond and viola. Let there be Light.