You should be able to tell from under the car if the parking brake cables are connected to each other.
In order to see that each of the rear cables is connected to the rear shoe, you have to pull off the wheel and drum. In this photo, on the one on the left, you can see the "parking brake cable and housing" coming into the drum at the bottom. Then it connects to the "parking brake lever" near the bottom. And the parking brake lever connects to the brake shoe near the top at a pivot point and it held in place with the "parking brake lever retaining clip". Then Directly below the wheel cylinder, running left to right there's a "parking brake link" that is trapped between the parking brake lever on one side and the other shoe on the other side.
Thats pretty much it for all the parking brake specific parts inside the wheel. There isn't any adjustment specifically for them inside the drums. Either they are connected correctly inside or they aren't.
Now, there is some adjustment for the entire drum brake assembly. This adjustment comes into play for normal braking and for the parking brake. Down at the bottom, there's a threaded cog, adjusting lever, adjuster spring, and a cable. The idea is that when you go in reverse and apply the brakes, the cable pulls up on the adjusting lever. Then you let off the brakes, the adjuster spring pulls the lever back down. If the lever was able to go up and skip a tooth on the cog on the adjusting screw, then when it comes back down, it will turn that cog a little bit which will expand and push the shoes outward more, closer to the drum itself. These adjuster screw assemblies are specific to each side of the car, one of them right handed threads and the other side left handed.
There happens to be a slot on the inside of the drum assembly covered with a rubber plug. So even with the drum and tire installed, you can pull that plug and use a flat screwdriver to rotate the cog. If you go too tight, you need 2 screwdrivers. First one you use to push the adjusting lever outwards off the cog, then the second one to rotate the cog. I like to adjust it so the shoes are as close as possible to the drum without dragging or rubbing. Jack up the rear of the car and the wheels should spin pretty freely.
I would verify the parking brake components are hooked up correctly inside the drum, then make sure the adjustment screw is set to expand the shoes out as far as possible without the shoes rubbing. Use a ruler or something under the car to make sure when you apply the parking brake, the cables at the shoes are both being pulled.