I found that having a fabric with metallic flecks will cause all kinds of havoc with FMQ. You can sew it, use straight stitching - either as a pattern or SITD, no problem. Use a regular stitch on the sewing machine like a serpentine, no problem, try FMQ? The minute you hit a fleck wrong, the trouble starts. You don't feel anything pulling, but stitches get skipped. Use a regular sandwich - no skips. Make a trial sandwich of flecked fabric - skips. Mostly on corners and curves, but will also skip on straight. As long as you had foot pressure and feed dogs, fabric just fine.