I had a piece of lint hang onto the thread as I was sewing with my Featherweight. It looked like felt. Then I noticed that my tension was really off. I turned the machine on its head and was surprised at the gunk that was under there that I really couldn't see when I just cleaned out the bobbin area. I needed to take off the needle plate. I hadn't been doing that. From now on, I'll be doing that a little oftener.