chevy van wiring

sounds like a grounding problem, my friend...sadly, you're going to have to break out a coarse wirebrush and wirebrush the frame and the beefy 1/0 cable from the battery...this way the light bulbs will get good ground...also the battery cable leading to the engine...all must pull 300 CCA assure that you've got a new battery (made from antimony alloy instead of lead nowadays) tho may start the vehicle okay puts a lot of strain on your alternator and regulator a cookin'~

the knock off labels on the top of your battery will indicate the date of the first charge....five years old is dodgy...ten years is like pushing a crippled old man thru the crosswalk~

Random lights getting power to them is not a ground issue, if the ground to the frame was bad then all the electrical would be affected not just a few lights. Chipmunks, squirrels, and mice chew in wires, trace the wires from the brake switch back to the loom and find where the wires are bad and replace them. It is most likely somewhere in the back on the drivers side. You are hitting the brakes and its feeding power to the reverse lights and the back door open switch, Could also have been pinched which will cause wire insulation to break.