It seems to me that the stock shrank moving the triggers and sear bar closer together; thus, requiring you to set the rear trigger to provide enough clearance for the sear to move. Play with it some more to try to determine if that is what is happening. If it is, I would try to remedy it by bending (hot, while the sear tip is clamped in a cold vise) the sear bar up very slightly. In my experience grinding the trigger bar and sear bar doesn't give you enough clearance. If this is the problem, there was probably way too little clearance to begin with.