I just purchased my first S&W in over 15 years. It's the M&P .40 Cal. model with a 4" barrel, and it looks very well designed. I paid a fair price for it, and it fits my hand perfectly. However, the trigger pull has a slight hitch just before firing.

I've been gunsmithing for over 30 years, but I've never even seen the inside of this model. Is there a known fix for this?