It is my guess that you are using cotton thread. Change to a poly thread and you should not have the breakage. I say this as that has been my experience with cotton thread. I quilt on a longarm machine; stitching in all different directions. Early in my business, I stitched a simple crosshatch border with cotton thread and found that I had thread breakage. A simple tug would break the cotton thread. Not many weeks ago I had a customer ask why I refused to use cotton thread when quilting. I handed her a cone of cottom thread and asked her to try to brake off a piece. She easily broke off a piece; then I gave her a poly wrapped poly cone and asked her to break off a piece. As much as she tried, she was unable to brake a piece off the poly cone. Questioned answered.