I also have a problem with this occasionally. I think whoever said to set the seam first is correct, I think it does work better. My quilting teacher always had us set the seam and I remember that they laid flat and I rarely had it twist. But later when I got really into quilting and was in a hurry, I didn't always set the seam. And that is when my problems started. Glad you mentioned this because now I will go back to setting the seams.