I have a Janome 7700. This is true for a normal foot - I am not certain about the dual feed.
What I have experienced is that the foot is angled up when I turn the corner. What I have learned is that you want something as thick as your quilt at the back of the foot so your foot is not trying to sew uphill. I have used a small pad of post it notes and also several layers of fabric. The item is only needed a few stitches and gets pushed away by the quilt.
Hope this works for you.