Brake light issue 87FC35

[xz3kg7]

During a recent trip I noticed my brake lights flickering, then often getting
stuck on. (I could see them at night in my camera). This coincides with a relay
in my overhead cabinet chattering.

Here is an experiment I tried. (slowed down w/o stepping on brake):
1. I am driving at highway speeds, then have to slow down for small town
2. I flip the switch and turn off cruise (i do NOT step on brake)
3. As I slow down, somewhere between 35 and 45, a relay in the overhead starts
chattering. The brake lights (as seen in camera) are now flickering,
corresponding to relay chattering.
4. Somewhere below 35, chattering stops, and brake lights are off (as they
should be).
5. Now let's say I speed back up, all the time WITHOUT stepping on brake. Again,
between 35 and 45 chattering starts.
6. Around 45, the chattering will stop, but OFTEN the BRAKE LIGHTS STAY ON. So
now, I am driving highway speeds with my brake lights on, and of course the
cruise will NOT engage. (I used to think I had a cruise problem).

So, here would be my questions:
1. First, does this chattering at certain speeds and then staying on make sense
to anyone?
2. Where is the brake switch? (I have tried pulling up on pedal)
3. Electrically, what is SUPPOSED to happen when I step on the brakes. (and
where would this overhead relay fit into what happens)

On the good news, just got back from a GREAT 10 days in Durango and Silverton
Colorado. Weather was fantastic, leaves were turning, and had a good time
Jeeping on the mountain 4x4 trails.

Thank you,
Alan Johnson
87FC35