Can't figure this out. My right rear brake light won't come on when the brakes are mashed, but the rear-driving lights do come on when the headlights are turned on. The left rear driving lights and the brake lights work fine. Both brakes and driving lights use the same bulbs, so it's not a loose wire/socket. Any ideas?

91 Integra

 

the bulbs are 2 stage bulbs... replace em