I think you have some wires missing insulation thus causing them to either short to ground or with each other. Which ones... that is the big question. One way to eliminate, not fix, the problem is..
Pull the fuse block and find the fuse that that rear light circuit uses. On the backside of the fuse panel/block you will see wires that are attached to that fuse. Pull the wire off one my one until those light shut off. Tape it and leave it off. Put it all back together. You have now isolated that part of the circuit and removed it. Deal with it later or not at all.
