What's not to fix?
Take a pointed center punch and ding the bottom of the dovetail in areas where it won't show when the slide is installed. If you do it carefully, you can also ding the sides/bottom of the dovetail to create some rough surface that will hold the sight in place. (The center where the punch hits is pushed down, but the surround area comes up, and it WILL tighten up the sight in the dovetail.)
As for cutting through into the bushing area -- it happens, depending entirely on how deep the dovetail must be cut to accept the new sight. A shallow dovetail wouldn't do it, but a deep one, which might be necessary, would.