Help with IK (From Merry Fragmas 3.0)

Hi all.

So I'm following the Merry Fragmas 3.0 tutorial and I just finished the IK part for the arms from Part II.
It kind of works.. I've set everything up just like in the tutorial and it looks just about right as long as the player isn't moving.. (The arms and hands are in the right position when the initial idle-animation is playing). But as soon as the player start moving and then stop everything looks weird, even when blending back to the idle animation.

What could be wrong here?

The picture to the left is when the player is walking forward or backwards, and the picture to the right is when the player has stopped moving.

Edit: The upper body twist when strafing (the animation is like that..).. Does that have anything to do with this? Can I somehow only make the legs animate and the upper body of the soldier stays static?