1976 Ford F150 pickup truck is having rear right brake light problem.
The rear right brake light does not come on during braking. it also
does not come on during hazard flasher use.

1. Rear, right and left RUNNING lights work fine.
2. Rear, right and left TURN signals work fine.
3. Rear LEFT brake light works fine
4. Rear RIGHT brake light does NOT work
5. Hazard lights work EXCEPT for RIGHT...which does NOT light up.

I have changed bulbs, flashers, and tested the socket and wiring up to
the connector under the tailgate and the bulbs etc are fine. Since
both directionals are working, and the directionals use the SAME
filament as the brake, I know it is something else.

Any ideas? How to chase down this gremlin. Spent all day
cutting/splicing/trying to islolate the problem to no avail.

Any ford techs on here can help?