Montero Sport 4wd problem
 

I got a 2002 Montero Sport a few months back and ran into a problem when shifting from all-wheel drive to 4-wheel drive. It just wiggles around and doesn't do anything. when I bought it, it had the same issue but the previous owner opened up the center console area and messed around with it for a bit and it started working again. I don't know when it stopped working again but it did. I don't know much about cars so if I could get a diagnosis and/or an estimate for how much this would cost to fix I would really appreciate it. Thank you in advance.