When the trigger will not return, the rebound spring is not "balanced" to the hammer spring. The only way these two lightened springs work properly is with an action that has been honed/polished, reduced friction, reduced spring requirements. You can not just throw reduced power springs, or back out the strain screw, and have everything work correctly. For the lighter springs you must reduce the internal friction. I'd take the gun back to stock hammer/rebound springs and see how you like it and go from there.

Stu