Thanks again for all the responses. Kinda fun trying to solve a puzzle via the internet that is ultimately insolvable unless you are hands on.
Here's some more clues:
To clarify the tug is a 2002 Tacoma, no factory tow package, but I bought it with a 2" receiver and a flat 4 connector. When I replaced the axel on the Trillium
about 5yrs. ago I added brakes
and hence had them wire in a 7pin connection in addition to the flat 4. Worked perfect. Installed new LED tail lights
, wired them backwards, figured it out, fixed it, and they worked perfectly for a couple years. Noticed that the raft trailer's tail lights
weren't working, but brake and turn signals were. It was an inaccessible, rusted mess. Took it in and had it rewired (no tug). Assumed it was fine (and it works perfectly when towed by a buddy's truck). Last fall
I noticed that the trillium's tail lights weren't working. Replaced both the male and female 7 pin connectors to no avail.
Now I just tow during the day light.
Living in the desert SW, corrosion is virtually non existent.