You are close. The spring is part of the parking brake assembly. That is a standard drum brake inside the rear brake rotor, and it uses standard-style shoe return springs. When they pull the shoes to retract them, that pulls on the parking brake cables, and those pull on the lever to hold it down.
While it is possible for a shoe return spring to break or become weak, it is much more common for a rear cable to become rusted in the partially-applied position. That reduces its ability to pull the lever all the way down.
To verify this, apply the parking brake, then release it slowly. Crawl underneath, just ahead of a rear wheel, and look for the casing that cable slides in. That casing will end where it is attached to the car body, close to where the links attach the axle to the body. It is typically only about two feet long. Look at the cable right where it exits that casing. If the first 1/2" is shiny, with no road dirt on it, that cable has not fully retracted. You will likely see if retract further if you flex the casing by hand.
If you see the cable retract further or all the way when you flex the casing, the only acceptable repair is to replace it. Do not even try to lubricate it. Any used-car dealer can tell you doing so will result in the car coming back on a tow truck with a parking brake that will not release.
Feb 20, 2021 at 12:39 PM
(Merged)