I have an Elna 6003 which is about 11 years old now. The instructions tell you to drop the feed dogs, put tension to 8 or 9 (which normally is at 5) and change stitch length to zero. I never have any issues when doing this. You might try it and see. It is not the darning foot causing the problem. I think you might need to increase tension on upper thread. That is why bobbin thread is lying straight. Good luck!