I worked in a fabric store, and we sold Janome machines. Part of my job was to make sure all the machines ran satisfactorily. There are only a couple of reason I can think of that would make a bird's nest in the bobbin area. 1. The machine could be threaded incorrecty. 2. Something is wrong with the bobbin area. 3. Incorrect bobbin for that machine. 4. The tension needs to be adjusted. I hope this helped. Good luck.