2002 Chevy Venture rear brake light problem

The lower rear brake lights on my Venture aren’t working, while the high light at the top of the door still works. I’ve replaced both circuit boards on the driver and passenger side, and all of the bulbs are fine. Any suggestions on what I might have missed along the way?

By the way, all f the other lights on the tail light assemblies work just fine. The only problem is with the brake lights.

Are the blinkers integrated into the brake lights? Same bulb, I mean? Something there to check into. I doubt it would be the flasher unit, but there’s normally some kind of module that controls the flashing, and which side gets constant power…that module is bypassed for the third brake light. It surely must cost less than replacing both light boards.