I have 3 Janome machines and have virtually no problems. I've sewn on 1 of those 3 for a couple of decades. I think the key to having no bobbin thread problems is to be careful when you begin to thread the bobbin to ensure there are no tangles or loops and then, as k3n said, when it's secured, stop the bobbin winding process, cut the thread end close to bobbin and finish the job. It should then automatically fill evenly from top to bottom and back up again, etc., BUT mine don't do that on their own, so I give the thread a gentle "assist" with my forefinger until the bobbin is full.