I am working on an older model "Ultimate 1". I broke a needle then noticed that the bobbin is dinged up. I have replaced the bobbin and needle but it continues to hit the bobbin occasionally, making a clanging noise but it continues to sew without breaking the needle. Surely there is an easy solution. It seems to be timed properly with each restart but continues to clang occasionally. Stitches look ok too. I have ruened 2 bobbins already.