[oldbadger]

Something to consider. Here is another thought as predicted earlier in this thread. Low and left groups are some times associated with a sudden trigger pull rather than a slow (sort of) steady (definitely) trigger press associated with a surprise break. Are you getting a surprise break? Is the trigger in question smooth and without any “grating” or metal on metal sensation? I have seen what you describe in some of my friends who see the sights line up on the desired point of impact and unconsciously say, “There it is” and pull the trigger rather than use a steady trigger press while keeping the sights on the desired point of impact as well as possible. Very few people can hold the pistol absolutely steady and will see the sight picture wobble. You may be able to see this fault in action by balancing a coin on the top of the slide and dry firing.....the coin should not fall off if you are doing it right. It may help to have a friend watch while you fire to see if you are moving the pistol at the time of the trigger press.
Hope this helps.