If you are fairly handy, you might polish the surface that the bend of the spring rides on in the back of the trigger. If you use a dremmel, it is unimportant but if you polish by hand with emery, go WITH the direction that the spring travels. If you've fired the gun a bit, you will see the rub marks where yu should concentrate your efforts. This should get you to a very slick, safe, robust set up. If you are still not there, take a needle nose pliers and bend BOTH legs equally, in very small increments, to relieve the torsional load applied. I've always perferred one or both of these methods in combination.
Ed