If you have a throat plate take that off and turn the wheel without thread anywhere and see where the needle is hitting. Or you may just find a mess of yuck under the throat plate and that will solve the problem. I had a problem with my mid arm--not Janome, that the spring that is on the inside of the bobbin area (not the bobbin itself) was broken on one end... it kept catching the thread and shredding it. I spent many an hour trying to find the reason for this. I found it by running my finger around inside the bobbin area and felt a sharp spot on the spring. When I took it out I could tell that it was my problem. New machine after I replaced that 3 dollar part.... good luck on your search and if you can't figure it out you may have to take your baby to the doctor for diagnosis...