any reason you are using the every tick instead of pinning the player to the box?
On a side note, usually when people walk/run up a hill, they don't lean back to match the angle of the hill they are walking up, then tend to try and remain straight up and down. But if you go over the tutorials I believe there is one on movement on angles, or it may be a forum post...
If your animations are not touching the ground when you walk on slopes, you may also want to look into adjusting the animation frames and/or the origin point used for the animation frames and make sure it matches l frames so that your collision box is also steady as well.