This is the time I would thread up "old clunky" my Singer treadle. It will sew through things my Bernina won't. Going over the welts in blue jeans pulled the needle right out of the holder on my Bernina but old clunky punched right through it. The only advice I can give is to use a jean stitch needle and lengthen your stitches? Hopefully someone else can come to your rescue.