Sorry, I messed up this reply, but I do agree you shouldn't have to try to remedy the bobbin issue yourself. You just came back from having the machine serviced. Call Bernina Headquarters to find another store for service and to mention what your problem is with the bobbin. They should call where you had the machine serviced to ask what's going on and that might alert your dealer to get on the ball. However, try rethreading the bobbin making procedure...go over all the steps and you might find out why your bobbin is stacking instead of winding correctly. Good luck.