If you have bought any new 66 bobbins they are made in China and the quality control is bad. If you buy 10 you
will probably throw 3 away. The diameters on some are too large and will cause the bobbin to drag. You will have
an intermittent problem when using these. Take every bobbin you buy and put it in the bobbin case and move it
around and spin it by hand to see if it is loose. If it is tight throw it away. I have had this problem mostly with the
new metal bobbins not the plastic ones.