OMG, please don't give up on your 15. I think they are the best. Sometimes I have that happen, but that is when I am going way way to fast. I usually turn my spool upside down as someone mentioned. Also, I use around felt piece on the botton of the spool. I agree to throw the bobbin out and even if you have to buy a new bobbin and case. There may be a bur inn it. I do like the idea of a washer on top. I have a brother that is notorious for this problem if I go to fast. It doesn't sound to me like a tension issue since your stitches are fine. I may suggest to change your type of thread, my old machines does not like gutterman and some brands. I know that may be silly to others but I find that to be true for me.