I just purchased a Consew 226 machine and am working on my first upholstery project. I am upholstering a console. I have glued 1/2" foam to the vinyl material. While sewing a seam (needle going through 2 layers of vinyl and 1/2" foam), the thread is cutting the foam and in some places the vinyl material. I have the stitch set at 5 and it looks like the thread tension for both upper thread and bobbin is fine (thread locks in the middle). Not sure why the material keeps getting cut. If I sew very slow, it doesn't cut but once the speed of the machine picks up, the material rips. I have adjusted the pressure of the walking foot. Can it be that I put too much glue on the material? Wrong size needles? Any suggestions would be appreciated.