Brake light/ turn signal

I'll bet the cheap light socket is not touching the base of the bulb. Try putting the turn signal on and then go push the bulb tighter into the socket. you can also remove the bulb and look down into the socket. It might be possible to bend the two electrical tabs up a bit so they make better contact when the bulb goes in.

I had a similar issue in on my 1986 and I could temporarily fix it by bending the tabs. In the end I had to pull the whole back panel down and replace the lights with some LED taillights.