Does your machine drop the feed dogs? Can you lessen the pressure of your presser foot? It sounds like your machine is shifting the fabric with too much pressure. I have a wonderful vintage Elna that has a self adjusting pressure foot and doesn't drop the feed dogs so for those reasons she doesn't quilt. My cure?? Another vintage machine - a 1956 Singer 301, which was born to FMQ, IMO. Vertical bobbin feeds the thread better, slant needle helps you see where you're going, feed dogs drop easily, a SITD foot available, adjustable presser foot, etc. I've heard there is no good walking foot for the 301, but so far I don't need one. To straight line quilt, I would leave the feeds up, reduce the pressure of the presser foot and use the stitch in the ditch foot.