96 Jetta GLS stoplights always on/brake pedal switch OK

Hello, on a 96 Jetta GLS w/ 98000 mi. my middle brake light (over rear window, "cyclops light") is always on as soon as I turn the key. I know that the brake pedal switch is not stuck, because if I don't have the key turned in the ignition, my L & R tailights & center brakelight will react normally to the brake pedal being depressed. I have pressed the switch by hand, & it's moving freely.
When I turn the ignition key, & the DTR headlights come on, so do my L&R tailights & the middle brakelight. Then, when I depress the brake pedal, the tailights & mid brakelight bighten up a little bit, & dim back down when the pedal is released. Besides the mid light always being on, the range of bright with pedal down to dim with pedal released is not as much as it should be in the L&R tailights.
It seems as if the DTR headlight function is "leaking" into the tailights & mid brakelight, because when that function (DTR) is not active, the tailights & mid brakelight go from fully off to fully on with the pedal, but as soon as the DTR headlights are on, so are all the rear lights. What's up, a bad relay or something?
Thanks