This can also happen when the wrong kind and/or size needle is used. When machine piecing I prefer to use Microtex Sharp or Quilting needles. Unless the fabric is thick I prefer a size 10 or 11 needle. Schmetz web site has great information on needle kinds and sizes. Basically, a fine sharp tip (not ball point) needle will slip through fabric without pushing it into the hole of the sole plate, but some fabrics (denim or chiffon) require specific needles. Learning about needles is a great investment of time that can and will save money. JMHO