One thing I discovered on some bobbins they don't have the cut out area that aligns a bobbin to the bobbin winder and that will cause a mess. The wrong size bobbin will also do that . The bobbin may look like it is the right size but it may not be. These are problems I have run into a few times. I will usually wind a hundred bobbins at a time and out of that 100 or so I will occasionally find one or two failures. I then toss those bobbins. I do use a good number of pre-wounds too.