bbeyes, I think we forget just how critical the mechanism is on our sewing machines, again going back to the workshop with Dawn Cameron-Dick I had no idea till then how tiny is the actual area that the stitches are formed, it is so tiny that it is a wonder that we even get a stitch when using cheapo linty threads. I now only use the best of threads and needles and am really meticulous in cleaning my machine, especially the bobbin area. Top tip, I found a super really small spiral brush that I use similar to the bottom one in this pic, think it came from a typewriter cleaning kit!