[spdbrake]

It sounds like you have the brake lights wired into the same circuit as your parking lights (which always come on at the 1st detent of the switch as does the dash lights).

If you've accidentally wired into the rear parking lights hot lead, thinking it was the ground for the brake light. It will backfeed what you are seeing occur. The brake lights will be getting its ground either thru the parking light or dash lights.

Or since the bulbs are twin contactor and if one of the socket connector base is twisted 90deg in the base the the brake could be running both circuits.