First off, I found the Range Finder before doing this quest so it was already in my inventory when I was instructed to retrieve it. Unfortunately it did not recognize that it was there so I had to go back to the kid in Freeside and buy it from him again. (Thought it was weird that he still had it even though I had already bought it from him).
Secondly, after getting the 2nd Range Finder, quit playing. When I started playing again, the quest was left in a sort of limbo with no locations to go to and no objectives to complete other than the overall objective of finding evidence. To fix this, I kept trading the Range Finder back and forth between my companion and I. Eventually it worked so I took it to Hidden Valley.
Third, once I got to the Elder, the game wouldn't allow me to talk to him unless I gave the Range Finder back to my companion. When I did that, the quest told me to get the Range Finder. So I did this over and over again but still nothing worked. My companion will walk up to the Elder like they're going to talk, but then nothing happens.
Honestly, I just want to turn this quest in, haha. I know the game has a lot of bugs but it's really fun and I just want to move on the next things in the game.