Oh my god. I got it solved. You cant simply take rooters head anywhere on the screen. You'll have to position yourself closely and precise which is not an easy taks because rooter is also walking around with you. Another example why this game is not very intuitive. You'll have to stand behind it. I wasn't able to take the head when I stood before him.
Again nothing what you may call a bug buts lets be honest: This really is not a good game design and has nothing to do with wrong resolutions.