Check width (side to side) and thickness (up and down). Use caliper to measure opening(s) in stock and wedge loop.
Use caliper to measure from top of barrel to center of opening in lug. Also measure from top of barrel to center of opening in side of stock. Are they offset?
Use strong light to check alignment. Might try using transfer medium/spotting compound on end of wedge to see where there is contact inside.
I file a little taper on the ends of my wedges to help them move into place. Not much, more of a rounding off of any squarish ends.