It could be your fabric. My friend and I had a puzzle one day. No matter what we did, neither of our sewing machines would sew some batiks that she had bought. We tried all types of settings, changed needles, tensions, bobbin threads and both machines, Babylock and Brother, would only sew a few stitches at a time. And, we weren't free motion quilting which is harder on the machines. A thought....I have an older Singer Golden Touch and Sew that will only free motion quilt if the quilt is taut in an embroidery hoop. My long arm won't stitch properly unless I have the quilt tension just right. Good luck! Please let us know what worked to fix your problem.