If I had to guess, somebody has had that gun apart. Either the trigger return slide/spring is installed wrong or, the hammer block was wedged back in there crooked. Have you taken it apart to see if something is wrong? If something was installed wrong, and you forced to through 700 rounds of dry fire and loosened the mainspring screw, it should be easy to tell now. there may be a couple gouges inside the gun and the sideplate.
If you are not comfortable with taking it apart, send it to Smith. Be prepared to pay for repairs. I doubt it left the factory that horribly fitted.