Moral: Read the instructions! If you have already purchased these and had the same experience, please follow the above and try again. They really DO WORK.
If you ever get "backlash" or "bird's nests" on the underside of free-motion quilting or embroidery, often due to changing direction at high speed, then you should try the Little Genie Magic Bobbin Washers. There's also some for Long Arm Machines.
Here's some photos I took to show you exactly what I mean by the little metal bobbin spring.