The slack adjuster on the parkin brake cable, simply does not adjust.
There is a cheat to make the handle apply brakes and not come up all the way to top.
Look in between the slot where the brake handle slides up, in the middle. You will see a flat metal tab in there.
Use a long handle screwdriver to hold that tab back when the handle is all the way up, and release handle downwards. Repeat as necessary until the parking brake is tight. 
This normally lasts a few times so I just carry the screwdriver in the glove box and it gets used often. It is what it is. It is a Jeep thing.
There should have been a recall on the cables/slack adjusters. 
Even with new rear brakes and ebrake shoes the adjuster remains a problem.

You'll need a long screwdriver.Lever off the panel which has the window switches on it,it's held in by 4 clips.Unscrew the 6 screws which hold the cd storage box in place.There are 4 inside it,and 2 at the back of it.
You'll now be able to see the bottom of the handbrake lever.In the middle of the mechanism there is a small right angled metal tab.
Pull the handbrake lever up,and then release it with the screwdriver forced against the tab to stop the tab moving.This will tighten up the cable.I had to do it twice to get it right.
Don't do it too much as it might lock the brakes on.