Am I missing a wire?

Any help and/or advice greatly appreciated. I’m working on a 1969 Airstream Caravel. I just need the marker lights, brake lights, and left and right turn signals to work using a 4-pin flat connecter. On the left side there is a red wire which I have matched up to the left turn Signal. Also on the left there are two green wires which I have matched to the marker lights. Also on the left is a black wire which I have matched to the backup light. Since I am only concerned with a 4-pin flat connecter I’m assuming I will not use this wire. On the right side I have two black wires which are matched to the backup light so, again, I will not use them. Also on the right are two green wires which I have matched to the marker lights. There is a brown wire on the right which I have matched to the right turn signal. Also on the right side is a red wire that is a loop. It is the same red wire that’s on the left side. In other words, if I pull the red wire on the left it pulls the loop out of the red wire on the right. On the front of the trailer there is a 10 gauge white wire which I have grounded to the frame and then continued to connect to the white wire coming from the tow vehicle. When I connect a bulb (1157?) to the turn signal wires on either side they work, although it seems not too bright. When I apply brakes the brake side of the bulb does not light. The bulbs have a red lead and a white lead. I’ve tried connecting one lead to the marker lights using a pigtail and the other lead to the turn/stop wire but that doesn’t work and I reversed them and that doesn’t work. It seems like I must be missing a wire on each side. I’ve watched a lot of video and read blogs but this is my third day and I just can’t figure it out. Thanks for any suggestions that will help me troubleshoot.