With the headlights off, all lights work normally.
With them on, there is current back feeding to the right signal indicator on the dash, and sometimes the right brake light works, sometimes it does not, but only when the headlights are on.
I cleaned both front and rear light sockets on the right and used dielectric grease. The ground on the front was confirmed with almost no voltage drop. The back socket where it connects to the light body is clean and greased, though I don't think this is the primary ground, if any ground at all. I ran a temporary ground from the right light socket to the left (which acts normally) but this did not solve the issue. I've attempted to find the proper ground for the RR lamps, with no avail.
What am I missing?