Re: RG3120 high e string problem!
I wouldn't recommend an amateur sanding the pocket, especially mahogany for the first time. Not that you can't do it.
I'd pull the trem out [with the strings on], take the strings off, and take it to Home Depot or Lowes and find a good pair of "cutting pliers". Grip the locator [curved] knife edge flush along the inside edge next to the saddle, and bite down hard before you pry the knife outward. Make sure the pliers are not slipping before prying, you only get one good shot at it virgin, and if you slide across the knife and it doesn't move, it will gouge and be very difficult to get good enough grip on it again. There is a detent in the knife that keeps it tight and it requires force to break the tension. You only need 1/2mm, but it's easy to tap it in if it's out too far when you install again.
That's the easiest way to fix that guitar.