I am wondering if you are jerking your hands slightly? It's a common mistake when learning FMQ..I was told it was because my mind was working faster than my machine..it's kind of like a car ..if you punch the gas pedal, there is a split second of hesitation before the car can catch up, but if you accelerate slow and evenly, your car responds well.I had to practice really hard at slowing down my mind and getting in sync with speed. I found it was happening to me when I had to change direction or angle of whatever I was stitching. Once you find your sweet spot between hands and machine, you'll love it!