i wanted to update my post here to let you know what the problems were:

- cleaned off the tangs, but that did not work
- changed *every* single fuse including the one that the lights reside on, but that didnt work
- changed the corner bulbs, swapped corner bulbs, etc., but that wasn't it.
- re-ground all the brown ground wires to a new place, that didn't work either

source of problem was corroded wires: yup, i sliced one down to see that the corrosion was pretty heavy. so i just cut about a foot off and soldered in new wires. voila. works like a charm now.