I just put in a trigger kit for my M&P 45, and thought I would run this issue I encountered by the forum.
I guess it's the striker pin (in the slide), the spring that came with the kit to replace the old stiffer one seemed a little unsafe to me. When checking the gun's safety function by pressing down the striker pin and then trying to push the firing pin forward, I was able to move the pin on several attempts. Other times it would still hold back the firing pin, but I did not feel comfortable with that, so I replaced the striker pin and left the old spring in the gun.
The trigger pull is still improved despite having to modify it this way. The pull is smooth and no longer has that spot where it sorta catches and required extra force to overcome. I am overall pleased.
I still have novak night sights to install. Any gunsmiths around Greeneville TN?