I am learning to sew using the book "Sew Fast, Sew Easy." My first project is a pillow. This pillow includes piping, and the instructions state to overlap the ends of the piping. I did this, and when I sewed over it, the machine had difficulty feeding and created a clump of thread on the other side. I have one more pillow to make (as a gift to my in-laws). What can I do to prevent the thread from bunching? It only happens when I go over the double layer of piping, and the machine appears to have difficulty moving beyond that area, even when I try to guide it.