Skipping occurs when the hook misses the top thread loop on the backside of the needle. The
needle will make an extra hole or holes in the fabric when this happens, but the stitch will be
longer. This is sometimes, if not often confused with a stitch regulation issue, because the
results appear very similar. The difference being that there will not be extra holes in the fabric
in the middle of a long stitch when it is a stitch regulation issue.
Skipping stitches is most often caused by the timing of the machine being out of proper adjustment.