Am not a gunsmith but seems lot of friends bring me guns that won't work. My standard repair is remove the wood spray it good with carb cleaner and blow out with the air hose. Cures a lot of ailments. Have replaced a lot of springs over the years too. Sometimes good cure sometimes not. Home shop spring jobs are mostly trial and error.
Recently bought a beater Parker just to learn how to take it apart. Stock off went through the cleaner & air hose routine, amazing what came out of it. Still gummy inside several applications of Kroll then the carb cleaner & air hose. It's nice and clean now. Apart and back together several times, going to take a lot more before I would be comfortable working on a nice Parker
Doubles are complicated and easy to mess up. If it was my Model 21 with no take apart experience I would send it to someone like Kirk, he has a flat rate clean and lube, while it's apart he will identify any issues. If it is a spring he's a lot more qualified to replace than most people.
Boats