I have found that the thread breaks when I am moving the quilt faster than the speed I'm sewing. I either need to slow down on the movement of put the pedal to the metal more. Another synptom of this is that you get eyelashes on the back, especially around curves. I use Connecting Threads Essentials & KIng Tut by Superior Threads. No difference in my results if I'm sewing at the correct speed for the movment.