Are you sewing from the center out or from the outside in? I have made several DP and a lot of stack n whack circles and had this problem sometimes. My home ec teacher taught us to "pet the kitty" and if it rubbed the ends of the fabric wrong, you should sew the other day. I think the instructions said to sew from the center out. Following the kitty analogy, this would be wrong. Well, I finally tried it the other way, and the results and difference have been astonishing. I am now sewing from the center out. Don't know what difference is, but working so much better. I don't know whether starting in the center distorts less since you have fabric to guide or what. When you go the other way, it gets down to a sliver and it is very easy to pull or relax so you don't get your fingers caught.