I had the same problem with my FW and 301 when I first got them but it was user error in both cases... Bobbin tension and needle threading issues. The 301 needle threads from right to left. Make sure your needle is inserted with the flat side facing left. And you MUST use the correct size bobbin with both. Also, make sure your bobbin tension is correct. The manuals will show you how to adjust bobbin tension. Hope this helps!