So why would the parking brake start having issues

Please check these guides and videos out.

Here are two videos to handle both 2500, 3500 and 1500 parking brake shoe replacements with diagrams below to help as well.

https://youtu.be/EMxfb9X3ywE

and

https://youtu.be/uo1RnATyEok

and

https://www.2carpros.com/articles/parking-brake-shoe-replacement

The park brake shoes must be adjusted before the park brake pedal is adjusted. Set the J 21177-A so that it contacts the inside diameter of the rotor. Position the J 21177-A over the shoe and the lining at the widest point. Turn the adjuster nut until the lining just contacts the J 21177-A. Repeat steps 1-3 for the opposite side. The clearance between the park brake shoe and the rotor is 0.6604 mm (0.026 in).

Please let us know if you need anything else to get the problem fixed.

You have to remove the caliper and rotor to replace the shoes for parking brake. They are similar to a regular drum brake. If you have a 25 series caliper remove is a little different

Most braking is done by front not rear. However if you don't have the adjuster correct in drum it won't work properly. The brakes have to be adjusted as well to just touch the drum where it will still spin. Recheck your work and try readjusting the brakes

You have to punch the piece out in backing plate to access the adjuster and it will spin in one direction. There are 3 different types of rear brakes so hopefully I sent the correct one.

If this is what you have the adjustment is where arrow is pointed for initial parking and brake adjustment which must be made with drum off. Yo need to measure at center of drum and shoe to get it close so drum would need to be turned.

REMOVAL & INSTALLATION

Front Cable
DRUM BRAKES

See Figure 1

Fig. 1: Front parking brake cable-C/K Series

1.Raise vehicle and support it with safety stands.
2.Remove adjusting nut from equalizer.
3.Remove retainer clip from rear portion of front cable at frame and from lever arm.
4.Disconnect front brake cable from parking brake pedal or lever assemblies. Remove front brake cable. On some models, it may assist installation of new cable if a heavy cord is tied to other end of cable in order to guide new cable through proper routing.

To install:

5.Install cable by reversing removal procedure.
6.Adjust parking brake.

Center Cable

1.Raise the vehicle on hoist.
2.Remove the adjusting nut from the equalizer.
3.Unhook the connector at each end and disengage the hooks and guides.
4.Install the new cable by reversing the removal procedure.
5.Adjust the parking brake.
6.Apply the parking brake 3 times with heavy pressure and repeat adjustment.

Rear Cable

See Figure 3

Fig. 3: Rear parking brake cable-C/K Series

1.Raise the vehicle and support it on safety stands.
2.Remove the rear wheel and brake drum.
3.Loosen the adjusting nut at the equalizer.
4.Disengage the rear cable at the connector.
5.Bend the retainer fingers at the backing plate.
6.Disengage the cable at the brake shoe operating lever.
7.Install the new cable.
8.Adjust the parking brake.

ADJUSTMENT

Duo-Servo Drum Brakes

The rear brakes serve a dual purpose. They are used as service brakes and as parking brakes. To obtain proper adjustment of the parking brake, the service brakes must first be properly adjusted as outlined earlier.

1.Apply the parking brake 4 clicks from the fully released position.
2.Raise and support the vehicle.
3.Loosen the locknut at the equalizer.
4.Tighten or loosen the adjusting nut until a moderate drag is felt when the rear wheels are rotated forward.
5.Tighten the locknut.
6.Release the parking brake and rotate the rear wheels. No drag should be felt. If even a light drag is felt, readjust the parking brake.
7.Lower the vehicle.

If a new parking brake cable is being installed, pre-stretch it by applying the parking brake hard about three times before making adjustments.

Leading/Trailing Drum Brakes

See Figures 4 and 5

1.Raise the rear of the truck and support it with safety stands. Remove the wheels and brake drum.
2.Measure the brake drum inside diameter.
3.Turn the adjuster nut until the brake shoe maximum diameter is 0.01-0.02 in. (0.25-50mm) less than the brake drum diameter.

Fig. 4: Parking brake adjusting screw-C/K Series

Fig. 5: Left side parking brake assembly-C/K Series

4.Make sure that the stops on the parking brake levers are against the edge of the brake shoe web. If the cable is holding the stops off the edge, loosen the adjustment.
5.Tighten the cable at the adjuster nut until the lever stops begin to move off the shoe webs.
6.Loosen the adjustment nut until the lever stops are just touching the shoe webs. There should be no more than 0.019 inch (0.5mm) clearance between the stops and the webs.
7.Install the drums and wheels.
8.Pump the brake pedal 30-35 times with normal force. Pause about 1 second between each stroke.
9.Depress the parking brake pedal 6 clicks. The wheels should be locked.
10.Release the parking brake. The wheels should rotate freely.

Axle may have been changed all pics and repair info I sent you is from GM repair manual you may want to try to make some hangers for the cable it doesnt have to be tight to cable just needs to be hold in place many auto parts stores have replacement hangers that are universal that you can use

You did not say what year the vehicle is. Guessing that you are having trouble removing the emergency brake from the shoe. Most common is a pin that goes through the secondary shoe, it is held on with a clip, to remove you have to pry the clip open so the pin will come out, then you can change shoes.

Put vice grips on the very end of the cable, on the metal end, then use sidecutters and pinch between the VGrips and the spring, push the spring back the grab tight with sidecutters, remove cable.