Yes, you need a darning foot or an open toed embroidery foot. Also, make sure the feed dogs are in the down postition. It sounds to me like this is the problem. Another thing is to get a straight stitch needle plate. It only has a round hole for the needle to go into instead of the wider hole of the zig-zag plate. What happens with the zig-zag is the thread gets pulled away from the race when you move it sideways in FMqing. The single small hole of the straight stitch plate eliminates this problem.