Just my 2 cents worth, but after running a 500 of these things in a large metropolitan county and buying mine from the agency, we found that the low shooters were often applying "extra grip" just as they pulled the trigger forcing the muzzle down in anticipation of recoil with this weapon. It happens sometimes too on double action revolvers.
The barrel missalinement in the frame of a 4043 to shoot a foot low would probably be detrimental to the gun. I have found the the S&W 4043 to be an excellent defensive pistol. So don't give up hope on it. Give it some practice and time.