I had this machine and there were several things that helped me: 1) setting the speed control lower 2) using a larger needle 3) had to play with the upper tension setting making it sure the thread was seated properly. Have you watched this Sewing Village youtube video on how to use this machine?
https://www.youtube.com/watch?v=uNHBEUtkUkI. Hope this helps. You've really got a wonderful machine unless something is wrong and it needs to be replaced. That happened to me and they replaced it. Good luck and happy sewing.