I believe I may know why this is happening. If your thread, cotton right? is breaking mid-seam, you may have left the cotton in a sunny place long enough to degrade the cotton in the sun. Sounds strange, but I had to get rid of a bunch years ago for doing the same thing. The side that faces the sun, is weakened by the sun's rays and creates a weakness every so many inches, viola! breaking threads every so often. Do not give the thread away or you are passing the problem on to another. Where are those quiltzillas when we have 'gifts' for them.... :thumbup: