Wiring Hell!

Bump your post.
"PO."
There’s your problem.
“Wiring” and “Hell” can be redundant.
Only thing I can tell you quick is that typically, the secondary filament in your tail light bulb is used by both the turn and brake function.
Moving the turn lever simply changes the circuitry.
Big help, huh?
And as far as the silver box, I have noticed this but never thought about it.
I’m curious. Possibly a resister. If it were a protective device I would think it would be a self-resetting thermal switch. But that is just a WAG.
I’ll go get my manuals and look if I have time. Maybe something is there.