I was going thru fits trying to solve a problem with my top stitches. Everything I did would not work. Tried rethreading, using new thread, reloading bobbin, different foot, every trick in the book. The I remembered the old saying of problem on top, check the bottom. Took it all apart and did another cleaning (already done that!). But, this time I also used a strong light and a mirror. Guess what? I found a tiny piece of thread caught underneath. It was causing all the problems!!!! Now, whenever I clean, I finish with bright light and the mirror!