Audi Repair: audi a6, audi a6 quattro, change good luck

Question
as a follow-up to last night's question---'99 audi a6 quattro 2.8 engine--brake light symbol is on though all brake lights are burning (no burned out bulbs or fuses that i can tell)--except now the third light in the back stays on when the headlights are on, and when the brake is depressed the front passenger parking light comes on.  the third brake light does darken when the brake is depressed, but it is staying on when the headlights are turned on.  the car is beeping every time the brake is depressed though i have had the brakes checked and the brake pads are only half worn.  i think i have covered everything.any ideas?  thank you.

Answer
hi
Sorry it took so long, but  I was trying to get some info. from other techs. Nobody run into a problem like this. We had some problems with shorted head light , which was turning fog light with low beam and turn signal with hi beam. (but this was in front)
Also , ones we had wrong brake light bulb, which was making many problems with tail lights.
So, I will start with checking bulbs or try to switch lights left to right ( connectors are the same) and see if anything change. ?????
good luck                         Greg