The transition between low Eb and Db (or vice versa), is troublesome for many flutists. If you can't do it smoothly, it doesn't mean that you are incompetent, it simply means that you need to practice doing it until it gets smoother. Also, you can try a little trick that many players use. Rub the tip of your RH pinky along the side of your nose where it joins your cheek. Most people have an excess of skin oil at that spot and rubbing it with your pinky will transfer some skin oil to the finger. That will make it slide more smoothly between the keys. As absurd as that may sound, try it. I think you will find that it helps.