When you uses the fast combo E on enemy + W in his position, tosses a Dagger in the air in the original position of Katarina. It's like when you press the W first and press E after, and the movement of Katarina are strange when this happen.
1.- Press E on enemy/minion first.
2.- After, fast, press W in his new position
3.- The Dagger of the W is in the position before we pressed E, or, in the original position