Can you check the trigger pull weight? Mine is about 5lbs on my FS pro.if yours is lower, say less the 4.5, Its likely it's been modified.

With the exception of the light reset, the trigger on my FS pro version is pretty nice. Not competition nice, but not bad at all especially since most of the grit is gone Does your trigger have an audible reset? Some people just addressed the reset and if yours does have a decent reset with an audible click (you can hardly feel or hear the stock reset, which btw is much improved on the newer versions and the shield), and the pull weight is still around 5lbs, then the reset parts may be the only part changed You can see a pic of the new parts on their site.