Dear god! I have the same problems with my two main break lights! Here is what I found! My wiring is good, fuse is good, both bulbs were replaced. Just playing around I found that the culprit was the turn signal switch! All of these following test (just in the sense of the word "test") were done both with the lights on and off, the car running and not, and with the key in the on position and not.
Turn the turn signal on in both directions When I turned the right TS on the right break light would quit working... is is supposed to! But when I thurned on the left turnsignal on both would stop working. Even if I just slightly applied pressure downward they would both stop working. If I applied just the slightest bit of preasure up both would begin to work again. In my case anyway. I am going to have to replace the TS switch.... that stinks, but it has to be done!
Source: My own experience!