I should add, I also confirmed continuity from the signal light grounds to fender ground points in the front (1 ohm), and from the trunk there is continuity between both ground contacts inside the signal sockets (I believe this was 4 ohms).
I also bent the pins in the sockets to make better contact with the bulbs while I was at it. Finally, I checked the center rear brake light above the rear passenger seats and cleaned the contacts there to rule that possibility out as well.
I also bent the pins in the sockets to make better contact with the bulbs while I was at it. Finally, I checked the center rear brake light above the rear passenger seats and cleaned the contacts there to rule that possibility out as well.