Was the rotation of the selector stiff and gritty before? Sometimes the location of the holes as well as the width of the selector can make a difference. The trigger rockers in the well and the rear shelf of the trigger rides against the round part of the selector and is "released" to firing on the flat on the selector. I've run into a couple of times trigger designs that if the pins drifted a bit changing the contact angle between the trigger and selector or a piece of debris--like a chunk of blown primer gets caught up in that area--it can create a wedge effect preventing easy rotation of the selector.
Stealing the picture from the link above--this is the contact area between the trigger and selector.
