I recently got and old Kenmore 158 zig zag machine. Cleaned oiled ect. Works great. Until you put fabric that isn't paper thin into the equation. Foot and thread tension good. Alignment is perfect. Moves smoothly without material and will do super thin perfectly. It acts like there isn't enough downward pressure on the mechanism above the needle. I'm at a loss. I pick up old machines frequently and this is new to me. Herlp please?