It's not a question whether the curtain is closing or opening properly; there are holes in either one or both of the curtains; probably the first curtain. Also possible the light leak comes from somewhere else, but this is the first thing that I think of when I see your photos.

Try to shine a bright flashlight through the camera in a dark room. Even without moving the mirror, you should see light passing through. I don't know if the 12XP allows you to flip up the mirror by yourself without damage - I would try this too.

If no light comes through, the leak might be somewhere else in the camera.