Hello, I recently bought a lg g2 from craigslist and realized that this problem was occurring. I tried fixing it by factory resetting and doing some other stuff, but it just wouldn't work. I then went on and downloaded an app called Dimly from the app store which lowers your screen brightness and have been using it for a while. The next day after, after coming back from school, I was using my phone and realized it was fixed! If you want, please try the app and see if it works for your phone.