I would also test it on regular fabric before going any more troubleshooting. The problem could very well be the minkee fabric. Sometimes when I do bags that are backed with the fusible fleece, I have a problem with the fabric feeding right with the walking foot because its grabbing the fleece. Minkee is kinda like fleece so thats why I suggest to at least try the walking foot with regular fabric on top and bottom. Just my opinion tho.