Audi a4 1.8tq brake lights not working

So I've searched many forums and have found about 10 threads about the same problem but none have solutions. Problem: my taillights went out the other day but the third brake light still works??? I'm gonna grab some fuses and bulbs this afternoon. I checked the fuse and it's fine...but might as well grab a pack and switch it just in case. Could it be the brake light switch??? Are there any relays that are tied only to the rear brake lights and not the third or is it possible to burn out half of a relay or brake switch??? The car is going to get replaced this spring...probably a newer a4. This one has many electrical gremlins and about 200k and it's a 1997. Mechanically it's perfect...never had a motor issue other than replacing the coil packs. Oh and the turn signals/reverse lights/ect. all work like they should. I'm stumped...please help. Thanks