Some machines just are finicky about bobbin winding. My Bernina's almost always are good and wind the bobbin fully and tightly and evenly. My Vikings have been more of a problem. I get some lop sided bobbin winding there and my friends who have Vikings also have problems. However, even lopsided, it usually stitches just fine. I use a Sidewinder Deluxe for my long arm. And it took a while to find the sweet tension on the winder itself. Now, most of the time I can wind decent bobbins. I have thought of having my Bernina do all the bobbin winding around here but really don't want to put the wear on the bobbin winding part. I did have a bobbin that was out of round. Sometimes they just come that way and sometimes it could be because I bounced it off the floor one too many times. I have purchased extra bobbins for all my machines....and actually, for the machines I can, an extra bobbin case. Oh, and also, make sure you have the thread fully inserted in any tension discs in the bobbin winding path.