65 dart turn signal wiring question.

You need to get the grounds straightened out first, as that can cause weird problems. On some cars the headlight/ parking lamp grounds all come together there with a bolt to the rad support.

Sometimes sockets like rear lamps can corrode/ rust, and you should consider cleaning them, and soldering a separate pigtail to them for grounding.

Also bulbs can cause you weird grief. Make CERTAIN they are the correct numbers, and that the sockets are not so bent/ damaged that they have been forced in with the wrong index. Also bulbs can have weird internal problems. Like, a filament can blow, and a "tag" of the filament can weld itself to the remaining filament, causing weird backflow in the system. I would test EACH bulb out of the sockets, and LOOK to make sure each filament lights separate as they should. You really need a "junk" tail/ turn socket for that