What you're seeing is a browser level bug that exists in webkit. If you check a current Firefox version or IE10 you'll notice what you've created works fine. Essentially you can't have a parallax nectar slider close to a parallax full width section. You can have as many parallax full width sections touching as you want, but the Nectar Slider uses a different method for animation (css3 based) and that causes glitches when in view of the old way the other sections use. The solution is either to simply get more distance between the two so that by the time you scroll to your parallax fullwidth section, the Nectar Slider is out of view or to disable the parallax on one of the two sections.
Thanks