Since you have ruled out all the mechanical questions, I have a couple of questions for you. Have you done a lot of FM quilting before or is this one of your first attempts? Do you have the parts of the quilt not under the needle sufficiently supported to avoid drag on your needle? I encountered exactly your problem. I brought my machine and project down the our open night at the LQS, and had one of the experienced ladies watch me. It turns out I was moving the quilt too fast for the speed of the machine/needle. I spent many more hours after that just practicing to get the rhythm just right. And, I still do a little bit of "practice" before quilting a new project just to get that timing back. The more I'm doing it, the more it really is like riding a bike.